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Amounts Reclassified from Accumulated OCI

Line Item in the Consolidated Statements of Comprehensive Income Where Net Income is Presented

Amounts reclassified from accumulated OCI for available-for-sale MBS

(Loss) gain on sale of agency securities, net

Periodic interest costs of interest rate swaps previously designated as hedges under GAAP, net

Interest expense

Total reclassifications

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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2013	Apr. 30, 2013
Entity Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	Q1
Entity Registrant Name	American Capital Agency Corp
Entity Central Index Key	0001423689
Entity Filer Category	Large Accelerated Filer
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		396,451,470
Trading Symbol	AGNC
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Assets:
Agency securities, at fair value	$ 74,874	$ 83,710
Agency securities transferred to consolidated variable interest entities, at fair value	1,421	1,535
Cash and cash equivalents	2,826	2,430
Restricted cash	499	399
Derivative assets, at fair value	480	301
Receivable for agency securities sold	734	0
Receivable under reverse repurchase agreements	12,291	11,818
Other assets	244	260
Total assets	93,369	100,453
Liabilities:
Repurchase agreements	66,260	74,478
Other debt	862	937
Payable for agency securities purchased	259	556
Derivative liabilities, at fair value	1,217	1,264
Dividend payable	499	427
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	12,548	11,763
Accounts payable and other accrued liabilities	82	132
Total liabilities	81,727	89,557
Stockholders' equity:
Preferred stock	167	167
Common stock	4	3
Additional paid-in capital	11,261	9,460
Retained earnings (deficit)	(557)	(289)
Accumulated other comprehensive income	767	1,555
Total stockholders' equity	11,642	10,896
Total liabilities and stockholders' equity	$ 93,369	$ 100,453

Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Available-for-sale Securities Pledged as Collateral	$ 70,094	$ 79,966
Assets Pledged included in Receivable for Securities Sold	$ 484	$ 0
Preferred Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Preferred Stock, Shares Issued	6.9	6.9
Preferred Stock, Shares Outstanding	6.9	6.9
Pref'd Stock Liquidation Preference	$ 173	$ 173
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	600.0	600.0
Common Stock, Shares, Issued	396.5	338.9
Common Stock, Shares, Outstanding	396.5	338.9

Consolidated Statements Of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest income:
Interest income	$ 547	$ 514
Interest expense	140	106
Net interest income	407	408
Other income, net:
Gain on sale of agency securities, net	(26)	216
(Loss) gain on derivative instruments and other securities, net	(98)	47
Total other income, net	(124)	263
Expenses:
Management fees	33	22
General and administrative expenses	9	6
Total expenses	42	28
Income before income tax	241	643
Income tax benefit, net	10	2
Net income	231	641
Dividend on preferred stock	3	0
Comprehensive income available to common shareholders	(560)	587
Net (loss) income (attributable) available to common shareholders	228	641
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	(837)	(106)
Unrealized (loss) gain on derivative instruments, net	49	52
Other comprehensive income (loss)	(788)	(54)
Comprehensive income	$ (557)	$ 587
Weighted average number of common shares outstanding-basic and diluted	356.2	240.6
Net income per common share - basic and diluted	$ 0.64	$ 2.66
Comprehensive income per share - basic and diluted	(1.57)	2.44
Dividends declared per common share	$ 1.25	$ 1.25

Consolidated Statement of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Interest Rate Swap [Member]
Balance, value at Dec. 31, 2011	$ 6,212	$ 0	$ 2	$ 5,937	$ (38)	$ 311
Balance, Preferred Stock, shares at Dec. 31, 2011		0.0
Balance, Common Stock, shares at Dec. 31, 2011			224.2
Net income	641				641
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	(106)					(106)
Unrealized (loss) gain on derivative instruments, net	52
Unrealized (loss) gain on derivative instruments, net \| Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]							$ 52
Issuance of common stock, value	2,205		$ 1	2,204
Issuance of common stock, shares			75.8
Common dividends declared	286				286
Balance, value at Mar. 31, 2012	$ 8,718	$ 0	$ 3	8,141	317	257
Balance, Preferred Stock, shares at Mar. 31, 2012		0.0
Balance, Common Stock, shares at Mar. 31, 2012			300.0
Other comprehensive income (loss):
Preferred Stock, Shares Issued	6.9
Balance, value at Dec. 31, 2012	$ 10,896	$ 167	$ 3	9,460	(289)	1,555
Balance, Preferred Stock, shares at Dec. 31, 2012	6.9	6.9
Balance, Common Stock, shares at Dec. 31, 2012	338.9		338.9
Net income	$ 231				231
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	(837)					(837)
Unrealized (loss) gain on derivative instruments, net	49
Unrealized (loss) gain on derivative instruments, net \| Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]	49						$ 49
Issuance of common stock, value	1,802		$ 1	1,801
Dividends, Preferred Stock	$ (3)
Issuance of common stock, shares	57.5		57.6
Common dividends declared	$ 496				496
Balance, value at Mar. 31, 2013	$ 11,642	$ 167	$ 4	$ 11,261	$ (557)	$ 767
Balance, Preferred Stock, shares at Mar. 31, 2013	6.9	6.9
Balance, Common Stock, shares at Mar. 31, 2013	396.5		396.5
Other comprehensive income (loss):
Preferred Stock, Shares Issued	6.9

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities:
Net income (loss)	$ 231	$ 641
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of agency securities premiums and discounts, net	134	100
Amortization of accumulated other comprehensive loss on interest rate swaps de-designated as qualifying hedges	49	52
Gain on sale of agency securities, net	26	(216)
Loss (gain) on derivative instruments and other securities, net	98	(47)
Increase in other assets	19	(70)
Increase in accounts payable and other accrued liabilities	(42)	12
Accretion of discounts on debt of consolidated variable interest entities	3	0
Net cash provided by operating activities	518	472
Investing activities:
Purchases of agency securities	(15,294)	(34,298)
Proceeds from sale of agency securities	19,568	8,196
Principal collections on agency securities	2,634	1,895
Purchases of U.S. Treasury securities	0	(2,016)
Proceeds from sale of U.S. Treasury securities	0	2,118
Proceeds from U.S. Treasury securities sold prior to purchase	10,001	11,000
Purchase of U.S. Treasury securities sold prior to purchase	(9,222)	(8,031)
Proceeds from reverse repurchase agreements	69,502	12,375
Payments made on reverse repurchase agreements	(69,975)	(15,223)
Net (payments) receipts on other derivative instruments not designated as qualifying hedges	(329)	(136)
Decrease in restricted cash	(100)	21
Net cash used in investing activities	6,785	(24,099)
Financing activities:
Proceeds from repurchase arrangements, net	96,511	93,962
Payments made on repurchase agreements	(104,729)	(71,827)
Repayments on other debt	(64)	(4)
Net proceeds from common stock issuances	1,802	2,205
Cash dividends paid	(427)	(314)
Net cash provided by financing activities	(6,907)	24,022
Net change in cash and cash equivalents	396	395
Cash and cash equivalents at beginning of period	2,430	1,367
Cash and cash equivalents at end of period	$ 2,826	$ 1,762

Unaudited Interim Consolidated Financial Statements	3 Months Ended
Unaudited Interim Consolidated Financial Statements	Mar. 31, 2013
Unaudited Interim Financials [Abstract]
Unaudited Interim Consolidated Financial Statements	Unaudited Interim Consolidated Financial Statements The interim consolidated financial statements of American Capital Agency Corp. (referred throughout this report as the “Company”, “we”, “us” and “our”) are prepared in accordance with U.S. generally accepted accounting principles (“GAAP”) for interim financial information and pursuant to the requirements for reporting on Form 10-Q and Article 10 of Regulation S-X. The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Actual results could differ from those estimates. Our unaudited consolidated financial statements include the accounts of our wholly-owned subsidiary, American Capital Agency TRS, LLC, and variable interest entities for which the Company is the primary beneficiary. Significant intercompany accounts and transactions have been eliminated. In the opinion of management, all adjustments, consisting solely of normal recurring accruals, necessary for the fair presentation of financial statements for the interim period have been included. The current period’s results of operations are not necessarily indicative of results that ultimately may be achieved for the year.

- Definition

Disclosure of accounting policy regarding (1) the principles it follows in consolidating or combining the separate financial statements, including the principles followed in determining the inclusion or exclusion of subsidiaries or other entities in the consolidated or combined financial statements and (2) its treatment of interests (for example, common stock, a partnership interest or other means of exerting influence) in other entities, for example consolidation or use of the equity or cost methods of accounting. The accounting policy may also address the accounting treatment for intercompany accounts and transactions, noncontrolling interest, and the income statement treatment in consolidation for issuances of stock by a subsidiary.

+ References

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+ Details

Organization	3 Months Ended
Organization	Mar. 31, 2013
Organization [Abstract]
Organization	Organization We were organized in Delaware on January 7, 2008, and commenced operations on May 20, 2008 following the completion of our initial public offering (“IPO”). Our common stock is traded on The NASDAQ Global Select Market under the symbol “AGNC”. We operate so as to qualify to be taxed as a real estate investment trust (“REIT”) under the Internal Revenue Code of 1986, as amended (the “Internal Revenue Code”). Therefore, substantially all of our assets, other than our taxable REIT subsidiary ("TRS"), consist of qualified real estate assets (as defined under the Internal Revenue Code). As a REIT, we are required to distribute annually 90% of our taxable net income. As long as we continue to qualify as a REIT, we will generally not be subject to U.S. federal or state corporate taxes on our taxable net income to the extent that we distribute all of our annual taxable net income to our stockholders. It is our intention to distribute 100% of our taxable income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent taxable year. We are externally managed by American Capital AGNC Management, LLC (our “Manager”), an affiliate of American Capital, Ltd. (“American Capital”). We earn income primarily from investing on a leveraged basis in agency mortgage-backed securities ("agency MBS"). These investments consist of residential mortgage pass-through securities and collateralized mortgage obligations (“CMOs”) for which the principal and interest payments are guaranteed by government-sponsored entities, such as the Federal National Mortgage Association (“Fannie Mae”) and the Federal Home Loan Mortgage Corporation (“Freddie Mac”), or by a U.S. Government agency, such as the Government National Mortgage Association (“Ginnie Mae”) (collectively referred to as “GSEs”). We may also invest in agency debenture securities issued by Freddie Mac, Fannie Mae or the Federal Home Loan Bank ("FHLB"). We refer to agency MBS and agency debenture securities collectively as "investment securities" and we refer to the specific investment securities in which we invest as our "investment portfolio". Our principal objective is to preserve our net asset value (also referred to as "net book value", "NAV" and "stockholders' equity") while generating attractive risk-adjusted returns for distribution to our stockholders through regular quarterly dividends from the combination of our net interest income and net realized gains and losses on our investments and hedging activities. We fund our investments primarily through short-term borrowings structured as repurchase agreements.

- Definition

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

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+ Details

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2013
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Investment Securities ASC Topic 320, Investments—Debt and Equity Securities (“ASC 320”), requires that at the time of purchase, we designate a security as held-to-maturity, available-for-sale or trading, depending on our ability and intent to hold such security to maturity. Securities classified as trading and available-for-sale are reported at fair value, while securities classified as held-to-maturity are reported at amortized cost. We may, from time to time, sell any of our investment securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our investment securities as available-for-sale. All securities classified as available-for-sale are reported at fair value, with unrealized gains and losses reported in accumulated other comprehensive income ("OCI"), a separate component of stockholders’ equity. Upon the sale of a security, we determine the cost of the security and the amount of unrealized gains or losses to reclassify out of accumulated OCI into earnings based on the specific identification method. Interest-only securities and inverse interest-only securities (collectively referred to as “interest-only securities”) represent our right to receive a specified proportion of the contractual interest flows of specific agency CMO securities. Principal-only securities represent our right to receive the contractual principal flows of specific agency CMO securities. Interest-only and principal-only securities are measured at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Our investments in interest-only and principal-only securities are included in agency MBS securities, at fair value on the accompanying consolidated balance sheets. We estimate the fair value of our investment securities based on a market approach using Level 2 inputs from third-party pricing services and non-binding dealer quotes derived from common market pricing methods. Such methods incorporate, but are not limited to, reported trades and executable bid and asked prices for similar securities, bench mark interest rate curves, such as the spread to the U.S. Treasury rate and interest rate swap curves, convexity, duration and the underlying characteristics of the particular security, including coupon, periodic and life caps, rate reset period, issuer, additional credit support and expected life of the security. Refer to Note 8 for further discussion of fair value measurements. We evaluate securities for other-than-temporary impairment (“OTTI”) on at least a quarterly basis, and more frequently when economic or market conditions warrant such evaluation. The determination of whether a security is other-than-temporarily impaired involves judgments and assumptions based on subjective and objective factors. When an investment security is impaired, an OTTI is considered to have occurred if (i) we intend to sell the investment security (i.e. a decision has been made as of the reporting date) or (ii) it is more likely than not that we will be required to sell the investment security before recovery of its amortized cost basis. If we intend to sell the security or if it is more likely than not that we will be required to sell the investment security before recovery of its amortized cost basis, the entire amount of the impairment loss, if any, is recognized in earnings as a realized loss and the cost basis of the security is adjusted to its fair value. We did not recognize any OTTI charges on our investment securities for the three months ended March 31, 2013 and 2012. Interest Income Interest income is accrued based on the outstanding principal amount of the investment securities and their contractual terms. Premiums and discounts associated with the purchase of investment securities are amortized or accreted into interest income over the projected lives of the securities, including contractual payments and estimated prepayments using the interest method in accordance with ASC Subtopic 310-20, Receivables—Nonrefundable Fees and Other Costs (“ASC 310-20”). We estimate long-term prepayment speeds of our agency securities using a third-party service and market data. The third-party service estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates and mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, volatility and other factors. We review the prepayment speeds estimated by the third-party service and compare the results to market consensus prepayment speeds, if available. We also consider historical prepayment speeds and current market conditions to validate the reasonableness of the prepayment speeds estimated by the third-party service and, based on our Manager’s judgment, we may make adjustments to their estimates. Actual and anticipated prepayment experience is reviewed quarterly and effective yields are recalculated when differences arise between (i) our previously estimated future prepayments and (ii) actual prepayments to date plus current estimated future prepayments. If the actual and estimated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. The yield on our adjustable rate securities further assumes that the securities reset at a rate equal to the underlying index rate in effect as of the date we acquired the security plus the stated margin. Derivative Instruments We use a variety of derivative instruments to economically hedge a portion of our exposure to market risks, including interest rate risk, prepayment risk and extension risk. The objective of our risk management strategy is to reduce fluctuations in net book value over a range of interest rate scenarios. In particular, we attempt to mitigate the risk of the cost of our variable rate liabilities increasing during a period of rising interest rates. The principal instruments that we use are interest rate swaps and options to enter into interest rate swaps (“interest rate swaptions”). We also utilize forward contracts for the purchase or sale of agency MBS securities on a generic pool, or to-be-announced, basis ("TBA contracts") and on a non-generic specified pool basis, and we utilize U.S. Treasury securities and U.S. Treasury futures contracts, primarily through short sales. We may also purchase or write put or call options on TBA securities and we may invest in other types of mortgage derivatives, such as interest-only securities, and synthetic total return swaps, such as the Markit IOS Synthetic Total Return Swap Index (“Markit IOS Index”). We may also enter into TBA contracts as a means of investing in and financing agency securities. Pursuant to TBA contracts, we agree to purchase, for future delivery, agency securities with certain principal and interest terms and certain types of collateral, but the particular agency securities to be delivered are not identified until shortly before the TBA settlement date. We also may choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting short position (referred to as a "pair off"), net settling the paired off positions for cash, and simultaneously purchasing a similar TBA contract for a later settlement date. This transaction is commonly referred to as a “dollar roll.” The agency securities purchased for a forward settlement date are typically priced at a discount to agency securities for settlement in the current month. This difference (or discount) is referred to as the “price drop.” The price drop is the economic equivalent of net interest carry income on the underlying agency securities over the roll period (interest income less implied financing cost) and is commonly referred to as "dollar roll income." Consequently, forward purchases of agency securities and dollar roll transactions represent a form of off-balance sheet financing. We account for derivative instruments in accordance with ASC Topic 815, Derivatives and Hedging (“ASC 815”). ASC 815 requires an entity to recognize all derivatives as either assets or liabilities in the balance sheet and to measure those instruments at fair value. Our derivative agreements generally contain provisions that allow for netting or setting off derivative assets and liabilities with each counterparty; however, we report related assets and liabilities on a gross basis in our consolidated balance sheets. Derivative instruments in a gain position are reported as derivative assets at fair value and derivative instruments in a loss position are reported as derivative liabilities at fair value in our consolidated balance sheets. Changes in fair value of derivative instruments and periodic settlements related to our derivative instruments are recorded in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Cash receipts and payments related to derivative instruments are classified in our consolidated statements of cash flows according to the underlying nature or purpose of the derivative transaction, generally in the investing section. The use of derivatives creates exposure to credit risk relating to potential losses that could be recognized in the event that the counterparties to these instruments fail to perform their obligations under the contracts. We attempt to minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Discontinuation of hedge accounting for interest rate swap agreements Prior to the third quarter of 2011, we entered into interest rate swap agreements typically with the intention of qualifying for hedge accounting under ASC 815. However, as of September 30, 2011, we elected to discontinue hedge accounting for our interest rate swaps. Upon discontinuation of hedge accounting, the net deferred loss related to our de-designated interest rate swaps remained in accumulated OCI and is being reclassified from accumulated OCI into interest expense on a straight-line basis over the remaining term of each interest rate swap. Interest rate swap agreements We use interest rate swaps to economically hedge the variable cash flows associated with borrowings made under our repurchase agreement facilities. Under our interest rate swap agreements, we typically pay a fixed rate and receive a floating rate based on one, three or six-month LIBOR ("payer swap") with terms up to 10 years, which has the effect of modifying the repricing characteristics of our repurchase agreements and cash flows on such liabilities. We estimate the fair value of interest rate swaps using a combination of inputs from counterparty and third-party pricing models to estimate the net present value of the future cash flows using a forward interest rate yield curve in effect as of the end of the measurement period. We also incorporate both our own and our counterparties’ nonperformance risk in estimating the fair value of our interest rate swaps. In considering the effect of nonperformance risk, we consider the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We purchase interest rate swaptions to help mitigate the potential impact of larger increases or decreases in interest rates on the performance of our investment portfolio (referred to as “convexity risk”). The interest rate swaptions provide us the option to enter into an interest rate swap agreement for a predetermined notional amount, stated term and pay and receive interest rates in the future. Our swaption agreements typically provide us the option to enter into a pay fixed rate interest rate swap, which we refer as “payer swaptions”. We may also enter into swaption agreements that provide us the option to enter into a receive fixed interest rate swap, which we refer to as "receiver swaptions". The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the swaption that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the swaption is reported in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income. If a swaption expires unexercised, the realized loss on the swaption would be equal to the premium paid. If we sell or exercise a swaption, the realized gain or loss on the swaption would be equal to the difference between the cash or the fair value of the underlying interest rate swap received and the premium paid. We estimate the fair value of interest rate swaptions using a combination of inputs from counterparty and third-party pricing models based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option, adjusted for non-performance risk, if any. TBA securities A TBA security is a forward contract for the purchase ("long position") or sale ("short position") of agency MBS at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific agency MBS delivered into the contract upon the settlement date, published each month by the Securities Industry and Financial Markets Association, are not known at the time of the transaction. We enter into TBA contracts as a means of hedging against short-term changes in interest rates. We may also enter into TBA contracts as a means of acquiring agency securities and we may from time to time utilize TBA dollar roll transactions to finance agency MBS purchases. We account for TBA contracts as derivative instruments since we cannot assert that it is probable at inception and throughout the term of the TBA contract that we will take physical delivery of the agency security upon settlement of the contract. We account for TBA dollar roll transactions as a series of derivative transactions. Gains, losses and dollar roll income associated with our TBA contracts and dollar roll transactions are recognized in our consolidated statements of comprehensive income in gain (loss) on derivative instruments and other securities, net. We estimate the fair value of TBA securities based on similar methods used to value our agency MBS securities. Forward commitments to purchase or sell specified agency MBS We enter into forward commitments to purchase or sell specified agency MBS from time to time as a means of acquiring assets or as a hedge against short-term changes in interest rates. We account for contracts for the purchase or sale of specified agency MBS securities as derivatives if the delivery of the specified agency MBS and settlement extends beyond the shortest period possible for that type of security. Realized and unrealized gains and losses associated with forward commitments accounted for as derivatives are recognized in our consolidated statements of comprehensive income in gain (loss) on derivative instruments and other securities, net. We estimate the fair value of forward commitments to purchase or sell specified agency MBS based on similar methods used to value agency MBS, as well as the remaining length of time of the forward commitment. U.S. Treasury securities We purchase or sell short U.S. Treasury securities and U.S. Treasury futures contracts to help mitigate the potential impact of changes in interest rates on the performance of our portfolio. We borrow securities to cover short sales of U.S. Treasury securities under reverse repurchase agreements. We account for these as securities borrowing transactions and recognize an obligation to return the borrowed securities at fair value on the balance sheet based on the value of the underlying borrowed securities as of the reporting date. Gains and losses associated with purchases and short sales of U.S. Treasury securities are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.

Investment Securities

3 Months Ended

Mar. 31, 2013

Available-for-sale Securities [Abstract]

Investment Securities

As of March 31, 2013, we had agency MBS at fair value of $76.3 billion, with a total cost basis of $75.1 billion. The net unamortized premium balance on our investment portfolio as of March 31, 2013 was $3.8 billion, including interest-only and principal-only strips. The following tables summarize our investments in agency MBS as of March 31, 2013 (dollars in millions):



	March 31, 2013
Agency MBS	Fannie Mae			Freddie Mac			Ginnie Mae			Total
Available-for-sale agency MBS:
Agency MBS, par	$	50,510		$	20,228		$	218		$	70,956
Unamortized discount	(20		)	—			—			(20		)
Unamortized premium	2,691			939			9			3,639
Amortized cost	53,181			21,167			227			74,575
Gross unrealized gains	1,044			330			6			1,380
Gross unrealized losses	(116		)	(60		)	—			(176		)
Total available-for-sale agency MBS, at fair value	54,109			21,437			233			75,779
Agency MBS remeasured at fair value through earnings:
Interest-only and principal-only strips, amortized cost ⁽¹⁾	463			50			—			513
Gross unrealized gains	24			1			—			25
Gross unrealized losses	(11		)	(11		)	—			(22		)
Total agency MBS remeasured at fair value through earnings	476			40			—			516
Total agency MBS, at fair value	$	54,585		$	21,477		$	233		$	76,295
Weighted average coupon as of March 31, 2013⁽²⁾	3.75		%	3.67		%	3.76		%	3.73		%
Weighted average yield as of March 31, 2013⁽³⁾	2.74		%	2.80		%	1.59		%	2.75		%
Weighted average yield for the three months ended March 31, 2013⁽³⁾	2.79		%	2.83		%	1.56		%	2.80		%

________________________


1.	The underlying unamortized principal balance (“UPB” or “par value”) of our interest-only agency MBS strips was $1.5 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of March 31, 2013. The par value of our principal-only agency MBS strips was $295 million as of March 31, 2013.


2.	The weighted average coupon includes the interest cash flows from our interest-only agency MBS strips taken together with the interest cash flows from our fixed-rate, adjustable-rate and CMO agency MBS as a percentage of the par value of our agency MBS (excluding the UPB of our interest-only securities) as of March 31, 2013.


3.	Incorporates a weighted average future constant prepayment rate assumption of 9% based on forward rates as of March 31, 2013.



	March 31, 2013
Agency MBS	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Fixed-Rate	$	73,649	$	1,355	$	(176	)	$	74,828
Adjustable-Rate	773		21		—			794
CMO	153		4		—			157
Interest-only and principal-only strips	513		25		(22		)	516
Total agency MBS	$	75,088	$	1,405	$	(198	)	$	76,295

As of December 31, 2012, we had agency MBS at fair value of $85.2 billion, with a total cost basis of $83.2 billion. The net unamortized premium balance on our investment portfolio as of December 31, 2012 was $4.4 billion, including interest-only and principal-only strips. The following tables summarize our investments in agency MBS as of December 31, 2012 (dollars in millions):



	December 31, 2012
Agency MBS	Fannie Mae			Freddie Mac			Ginnie Mae			Total
Available-for-sale agency MBS:
Agency MBS, par	$	58,912		$	19,336		$	238		$	78,486
Unamortized premium	3,208			948			10			4,166
Amortized cost	62,120			20,284			248			82,652
Gross unrealized gains	1,585			481			6			2,072
Gross unrealized losses	(18		)	(7		)	—			(25		)
Available-for-sale agency MBS, at fair value	63,687			20,758			254			84,699
Agency MBS remeasured at fair value through earnings:
Interest-only and principal-only strips, amortized cost ⁽¹⁾	486			55			—			541
Gross unrealized gains	26			1			—			27
Gross unrealized losses	(9		)	(13		)	—			(22		)
Agency MBS remeasured at fair value through earnings	503			43			—			546
Total agency MBS, at fair value	$	64,190		$	20,801		$	254		$	85,245
Weighted average coupon as of December 31, 2012 ⁽²⁾	3.70		%	3.67		%	3.77		%	3.69		%
Weighted average yield as of December 31, 2012 ⁽³⁾	2.62		%	2.61		%	1.60		%	2.61		%
Weighted average yield for the year ended December 31, 2012 ⁽³⁾	2.83		%	2.83		%	1.63		%	2.82		%

________________________


1.	The UPB of our interest-only securities was $1.7 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of December 31, 2012. The par value of our principal-only agency MBS strips was $302 million as of December 31, 2012.


2.	The weighted average coupon includes the interest cash flows from our interest-only securities taken together with the interest cash flows from our fixed-rate, adjustable-rate and CMO securities as a percentage of the par value of our agency securities (excluding the UPB of our interest-only securities) as of December 31, 2012.


3.	Incorporates a weighted average future constant prepayment rate assumption of 11% based on forward rates as of December 31, 2012.



	December 31, 2012
Agency MBS	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Fixed-Rate	$	81,617	$	2,043	$	(25	)	$	83,635
Adjustable-Rate	865		26		—			891
CMO	170		3		—			173
Interest-only strips	541		27		(22		)	546
Total agency MBS	$	83,193	$	2,099	$	(47	)	$	85,245

As of March 31, 2013 and December 31, 2012, we did not have investments in agency debenture securities.

The actual maturities of our agency MBS securities are generally shorter than the stated contractual maturities. Actual maturities are affected by the contractual lives of the underlying mortgages, periodic contractual principal payments and principal prepayments. As of March 31, 2013 and December 31, 2012, our weighted average expected constant prepayment rate (“CPR”) over the remaining life of our aggregate agency MBS portfolio was 9% and 11%, respectively. Our estimates differ materially for different types of securities and thus individual holdings have a wide range of projected CPRs. We estimate long-term prepayment assumptions for different securities using a third-party service and market data. The third-party service estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates and mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, volatility and other factors. We review the prepayment speeds estimated by the third-party service and compare the results to market consensus prepayment speeds, if available. We also consider historical prepayment speeds and current market conditions to validate reasonableness. As market conditions may change rapidly, we may make adjustments for different securities based on our Manager's judgment. Various market participants could use materially different assumptions.

The following table summarizes our agency MBS classified as available-for-sale as of March 31, 2013 and December 31, 2012 according to their estimated weighted average life classification (dollars in millions):



	March 31, 2013								December 31, 2012
Estimated Weighted Average Life of Agency MBS Classified as Available-for-Sale ⁽¹⁾	Fair Value		Amortized Cost		Weighted Average Coupon		Weighted Average Yield		Fair Value		Amortized Cost		Weighted Average Coupon		Weighted Average Yield
≤ 3 years	279		272		4.54	%	3.01	%	1,119		1,108		4.18	%	2.14	%
> 3 years and ≤ 5 years	17,428		16,835		3.76	%	2.67	%	27,448		26,750		3.36	%	2.29	%
> 5 years and ≤10 years	49,750		49,132		3.68	%	2.76	%	54,054		52,735		3.69	%	2.75	%
> 10 years	8,322		8,336		2.96	%	2.65	%	2,078		2,059		3.44	%	2.65	%
Total	$	75,779	$	74,575	3.62	%	2.73	%	$	84,699	$	82,652	3.59	%	2.59	%

_______________________


1.	Excludes interest and principal-only strips.

The weighted average life of our interest-only strips was 6.0 and 5.7 years as of March 31, 2013 and December 31, 2012, respectively. The weighted average life of our principal-only strips was 7.0 and 6.4 years as of March 31, 2013 and December 31, 2012, respectively.

Our agency securities classified as available-for-sale are reported at fair value, with unrealized gains and losses excluded from earnings and reported in accumulated OCI. The following table summarizes changes in accumulated OCI, a separate component of stockholders equity, for our available-for-sale securities for the three months ended March 31, 2013 and 2012 (in millions):



Agency Securities Classified as Available-for-Sale	Beginning Accumulated OCI Balance		Unrealized Gains and (Losses), Net		Reversal of Prior Period Unrealized (Gains) and Losses, Net on Realization		Ending Accumulated OCI Balance
Three months ended March 31, 2013	$	2,041	(863	)	26		$	1,204
Three months ended March 31, 2012	$	1,002	110		(216	)	$	896

The following table presents the gross unrealized loss and fair values of our available-for-sale agency securities by length of time that such securities have been in a continuous unrealized loss position as of March 31, 2013 and December 31, 2012 (in millions):



	Unrealized Loss Position For
	Less than 12 Months					12 Months or More					Total
Agency Securities Classified as Available-for-Sale	Estimated Fair Value		Unrealized Loss			Estimated Fair Value		Unrealized Loss			Estimated Fair Value		Unrealized Loss
March 31, 2013	$	25,963	$	(174	)	$	84	$	(2	)	$	26,047	$	(176	)
December 31, 2012	$	8,430	$	(25	)	$	—	$	—		$	8,430	$	(25	)

As of March 31, 2013, we did not intend to sell any of these agency securities and we do not believe it is more likely than not we will be required to sell the agency securities before recovery of their amortized cost basis. The unrealized losses on these agency securities are not due to credit losses given the government-sponsored entity or government guarantees, but are rather due to changes in interest rates and prepayment expectations.

Gains and Losses

The following table is a summary of our net (loss) gain from the sale of agency MBS for the three months ended March 31, 2013 and 2012 (in millions):



	Three Months Ended
Agency MBS	March 31, 2013			March 31, 2012
Agency MBS sold, at cost	$	(20,328	)	$	(9,243	)
Proceeds from agency MBS sold ⁽¹⁾	20,302			9,459
Net (loss) gain on sale of agency MBS	$	(26	)	$	216

Gross gain on sale of agency MBS	$	87		$	220
Gross loss on sale of agency MBS	(113		)	(4		)
Net (loss) gain on sale of agency MBS	$	(26	)	$	216

________________________


1.	Proceeds include cash received during the period, plus receivable for agency MBS sold during the period as of period end.

For the three months ended March 31, 2013 and 2012, we recognized an unrealized loss of $1 million and an unrealized gain of $1 million, respectively, in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income for the change in value of investments in interest-only and principal-only strips, net of prior period reversals. For the three months ended March 31, 2013 and 2012, there were no sales of interest-only or principal-only securities.

Pledged Assets

The following tables summarize our assets pledged as collateral under repurchase agreements, debt of consolidated VIEs, derivative agreements and prime broker agreements by type, including securities pledged related to securities sold but not yet settled, as of March 31, 2013 and December 31, 2012 (in millions):



	March 31, 2013
Assets Pledged	Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements		Total
Agency MBS - fair value	$	69,537	$	1,421	$	812	$	229	$	71,999
Accrued interest on pledged securities	196		4		2				202
Restricted cash	—		—		116		383		499
Total	$	69,733	$	1,425	$	930	$	612	$	72,700



	December 31, 2012
Assets Pledged	Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements		Total
Agency MBS - fair value	$	78,400	$	1,535	$	1,065	$	501	$	81,501
Accrued interest on pledged securities	217		5		3		1		226
Restricted cash	—		—		249		150		399
Total	$	78,617	$	1,540	$	1,317	$	652	$	82,126

The following table summarizes our securities pledged as collateral under repurchase agreements and debt of consolidated VIEs by remaining maturity, including securities pledged related to sold but not yet settled securities, as of March 31, 2013 and December 31, 2012 (in millions):



	March 31, 2013						December 31, 2012
Securities Pledged by Remaining Maturity of Repurchase Agreements and Debt of Consolidated VIEs	Fair Value of Pledged Securities		Amortized Cost of Pledged Securities		Accrued Interest on Pledged Securities		Fair Value of Pledged Securities		Amortized Cost of Pledged Securities		Accrued Interest on Pledged Securities
Agency MBS:
Less than 30 days	$	28,076	$	27,572	$	80	$	29,284	$	28,525	$	82
31 - 59 days	14,020		13,774		39		21,716		21,251		58
60 - 90 days	7,321		7,241		21		16,188		15,780		45
Greater than 90 days	21,541		21,220		60		12,747		12,447		37
Total agency MBS	$	70,958	$	69,807	$	200	$	79,935	$	78,003	$	222

As of March 31, 2013 and December 31, 2012, none of our repurchase agreement borrowings backed by agency MBS were due on demand or mature overnight.

Securitizations and Variable Interest Entities

As of March 31, 2013 and December 31, 2012, we held investments in CMO trusts, which are variable interest entities ("VIEs"). We have consolidated certain of these CMO trusts in our consolidated financial statements where we have determined we are the primary beneficiary of the trusts. All of our CMO securities are backed by fixed or adjustable-rate agency MBS. Fannie Mae or Freddie Mac guarantees the payment of interest and principal and acts as the trustee and administrator of their respective securitization trusts. Accordingly, we are not required to provide the beneficial interest holders of the CMO securities any financial or other support. Our maximum exposure to loss related to our involvement with CMO trusts is the fair value of the CMO securities and interest and principal-only securities held by us, less principal amounts guaranteed by Fannie Mae and Freddie Mac.

As of March 31, 2013 and December 31, 2012, the fair value of our CMO securities and interest and principal-only securities, excluding the consolidated CMO trusts discussed below, was $673 million and $719 million, respectively, or $1.2 billion and $1.3 billion, respectively, including the net asset value of our consolidated CMO trusts discussed below. Our maximum exposure to loss related to our CMO securities and interest and principal-only securities, including our consolidated CMO trust, was $316 million and $343 million as of March 31, 2013 and December 31, 2012, respectively.

In connection with the consolidated trusts, as of March 31, 2013 and December 31, 2012, we recognized agency securities with a total fair value of $1.4 billion and $1.5 billion, respectively, and debt, at fair value of $862 million and $937 million, respectively, in our accompanying consolidated balance sheets. As of March 31, 2013 and December 31, 2012, such agency securities had an aggregate unpaid principal balance of $1.3 billion and $1.4 billion, respectively, and such debt had an aggregate unpaid principal balance of $844 million and $908 million, respectively. During the three months ended March 31, 2013 and 2012, we recognized a net gain of $13 million and $0, respectively, from debt of consolidated VIEs re-measured at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income. Our involvement with the consolidated trusts is limited to the agency securities transferred by us upon the formation of the trusts and the CMO securities subsequently held by us. There are no arrangements that could require us to provide financial support to the trusts.

Repurchase Agreements And Other Debt

3 Months Ended

Mar. 31, 2013

Disclosure of Repurchase Agreements [Abstract]

Repurchase Agreements And Other Debt

Repurchase Agreements and Other Debt

We pledge certain of our agency securities as collateral under repurchase arrangements with financial institutions, the terms and conditions of which are negotiated on a transaction-by-transaction basis. Interest rates on these borrowings are generally based on LIBOR plus or minus a margin and amounts available to be borrowed are dependent upon the fair value of the securities pledged as collateral, which fluctuates with changes in interest rates, type of security and liquidity conditions within the banking, mortgage finance and real estate industries. In response to declines in fair value of pledged securities, lenders may require us to post additional collateral or pay down borrowings to re-establish agreed upon collateral requirements, referred to as margin calls. As of March 31, 2013 and December 31, 2012, we have met all margin call requirements.

The following table summarizes our borrowings under repurchase arrangements and weighted average interest rates classified by original maturities as of March 31, 2013 and December 31, 2012 (dollars in millions):



	March 31, 2013					December 31, 2012
Original Maturity	Repurchase Agreements		Weighted Average Interest Rate		Weighted Average Days to Maturity	Repurchase Agreements		Weighted Average Interest Rate		Weighted Average Days to Maturity
Agency MBS:
≤ 1 month	$	8,059	0.41	%	13	$	4,011	0.48	%	13
> 1 to ≤ 3 months	29,461		0.42	%	30	28,307		0.49	%	37
> 3 to ≤ 6 months	11,173		0.48	%	68	24,303		0.49	%	63
> 6 to ≤ 9 months	4,436		0.49	%	140	5,222		0.54	%	79
> 9 to ≤ 12 months	8,063		0.58	%	216	7,813		0.58	%	222
> 12 to ≤ 24 months	2,099		0.63	%	469	1,917		0.65	%	564
> 24 to ≤ 36 months	2,767		0.67	%	872	2,803		0.69	%	963
> 36 months	202		0.74	%	1,532	102		0.73	%	1,751
Total agency MBS	$	66,260	0.47	%	118	$	74,478	0.51	%	118

As of March 31, 2013 and December 31, 2012, we did not have an amount at risk with any repurchase agreement counterparty greater than 3% and 4% of our stockholders’ equity, respectively.

As of March 31, 2013 and December 31, 2012, debt of consolidated VIEs, at fair value ("other debt") was $862 million and $937 million, respectively. As of March 31, 2013 and December 31, 2012, our other debt had a weighted average interest rate of LIBOR plus 42 and 43 basis points and a principal balance of $844 million and $908 million, respectively. The actual maturities of our other debt are generally shorter than the stated contractual maturities. The actual maturities are affected by the contractual lives of the underlying agency MBS securitizing our other debt and periodic principal prepayments of such underlying securities. The estimated weighted average life of our other debt as of March 31, 2013 was 5.7 years.

As of March 31, 2013, we also had net forward purchase commitments, including TBA dollar roll transactions, outstanding of $27.3 billion, at cost (see Notes 3 and 6). Forward purchase commitments and TBA dollar roll transactions represent a form of off-balance sheet financing. Pursuant to ASC 815, we typically account for such transactions as one or more series of derivative transactions and, consequently, they are not reflected in our on-balance sheet debt and leverage ratios.

Derivative and Other Hedging Instruments

3 Months Ended

Mar. 31, 2013

Derivative Asset, Fair Value, Net [Abstract]

Derivative and Other Hedging Instruments

In connection with our risk management strategy, we hedge a portion of our interest rate risk by entering into derivative and other hedging instrument contracts. We may enter into agreements for interest rate swaps, interest rate swaptions, interest rate cap or floor contracts and futures or forward contracts. We may also purchase or short TBA and U.S. Treasury securities, purchase or write put or call options on TBA securities or we may invest in other types of mortgage derivative securities, such as interest-only securities, and synthetic total return swaps, such as the Markit IOS Index. Our risk management strategy attempts to manage the overall risk of the portfolio, reduce fluctuations in book value and generate additional income distributable to stockholders. For additional information regarding our derivative instruments and our overall risk management strategy, please refer to the discussion of derivative and other hedging instruments in Note 3.

Prior to September 30, 2011, our interest rate swaps were typically designated as cash flow hedges under ASC 815; however, as of September 30, 2011, we elected to discontinue hedge accounting for our interest rate swaps in order to increase our funding flexibility. For the three months ended March 31, 2013 and 2012, we reclassified $49 million and $52 million, respectively, of net deferred losses from accumulated OCI into interest expense related to our de-designated interest rate swaps and recognized an equal, but offsetting, amount in other comprehensive income. Our total net periodic interest costs on our swap portfolio were $133 million and $91 million for the three months ended March 31, 2013 and 2012, respectively. The difference of $84 million and $39 million for the three months ended March 31, 2013 and 2012, respectively, is reported in our accompanying consolidated statement of comprehensive income in gain (loss) on derivative instruments and other securities, net. As of March 31, 2013, the remaining net deferred loss in accumulated OCI related to de-designated interest rate swaps was $(437) million and will be reclassified from OCI into interest expense over a remaining weighted average period of 2.7 years (see Note 9). The net deferred loss expected to be reclassified from OCI into interest expense over the next twelve months is $184 million as of March 31, 2013.

For the three months ended March 31, 2013 and 2012 and as of March 31, 2013 and December 31, 2012, none of our derivative instruments were designated as cash flow hedges under ASC 815.

Derivative Assets (Liabilities), at Fair Value

The table below summarizes fair value information about our derivative assets and liabilities as of March 31, 2013 and December 31, 2012 (in millions):



Derivatives Instruments	Balance Sheet Location	March 31, 2013			December 31, 2012
Interest rate swaps	Derivative assets, at fair value	$	56		$	14
Payer swaptions	Derivative assets, at fair value	332			171
Purchase of TBA and forward settling agency securities	Derivative assets, at fair value	86			116
Sale of TBA and forward settling agency securities	Derivative assets, at fair value	6			—
		$	480		$	301
Interest rate swaps	Derivative liabilities, at fair value	$	(1,100	)	$	(1,243	)
U.S. Treasury futures - short	Derivative liabilities, at fair value	(14		)	—
Purchase of TBA and forward settling agency securities	Derivative liabilities, at fair value	(95		)	(1		)
Sale of TBA and forward settling agency securities	Derivative liabilities, at fair value	(8		)	(20		)
		$	(1,217	)	$	(1,264	)

Additionally, as of March 31, 2013 and December 31, 2012, we had obligations to return U.S. Treasury securities borrowed under reverse repurchase agreements accounted for as securities borrowing transactions at a fair value of $12.5 billion and $11.8 billion, respectively. The borrowed securities were used to cover short sales of U.S. Treasury securities from which we received total proceeds of $12.5 billion and $11.7 billion, respectively. The change in fair value of the borrowed securities is recorded in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.

The following tables summarize our interest rate swap agreements outstanding as of March 31, 2013 and December 31, 2012 (dollars in millions):



	March 31, 2013
Interest Rate Swaps ⁽¹⁾	Notional Amount		Average Fixed Pay Rate		Average Receive Rate		Net Estimated Fair Value			Average Maturity (Years)
Three years or less	$	14,950	1.29	%	0.25	%	$	(309	)	2.0
Greater than 3 years and less than/equal to 5 years	19,750		1.41	%	0.27	%	(535		)	4.0
Greater than 5 years and less than/equal to 7 years	6,100		1.59	%	0.32	%	(145		)	6.0
Greater than 7 years and less than/equal to 10 years	7,250		1.89	%	0.31	%	(37		)	9.1
Greater than 10 years	3,200		2.17	%	0.28	%	(18		)	10.3
Total Payer Interest Rate Swaps	$	51,250	1.51	%	0.28	%	$	(1,044	)	4.8

________________________


1.	Amounts include forward starting swaps of $5.2 billion ranging up to 6 months from March 31, 2013.



	December 31, 2012
Interest Rate Swaps ⁽¹⁾	Notional Amount		Average Fixed Pay Rate		Average Receive Rate		Net Estimated Fair Value			Average Maturity (Years)
Three years or less	$	14,600	1.23	%	0.26	%	$	(294	)	2.0
Greater than 3 years and less than/equal to 5 years	20,250		1.48	%	0.29	%	(666		)	4.1
Greater than 5 years and less than/equal to 7 years	5,600		1.53	%	0.34	%	(163		)	6.1
Greater than 7 years and less than/equal to 10 years	5,200		1.89	%	0.35	%	(113		)	9.2
Greater than 10 years	1,200		1.79	%	0.31	%	7			10.2
Total Payer Interest Rate Swaps	$	46,850	1.46	%	0.29	%	$	(1,229	)	4.4

________________________


1.	Amounts include forward starting swaps of $1.7 billion ranging up to four months from December 31, 2012.

The following tables summarize our interest rate swaption agreements outstanding as of March 31, 2013 and December 31, 2012 (dollars in millions):



	March 31, 2013
	Option					Underlying Swap
Payer Swaptions	Cost		Fair Value		Average Months to Expiration	Notional Amount		Average Fixed Pay Rate		Average Receive Rate	Average Term (Years)
One year or less	$	169	$	91	7	$	12,100	2.49	%	1M / 3M LIBOR	8.4
Greater than 1 year and less than/equal to 2 years	81		52		17	4,200		2.81	%	3M LIBOR	6.8
Greater than 2 years and less than/equal to 3 years	139		137		32	5,000		3.42	%	3M LIBOR	8.5
Greater than 3 years and less than/equal to 4 years	12		13		43	450		3.20	%	3M LIBOR	6.1
Greater than 4 years and less than/equal to 5 years	37		39		57	1,150		3.51	%	3M LIBOR	4.5
Total/Wtd Avg	$	438	$332		17	$	22,900	2.81	%	1M / 3M LIBOR	7.9



	December 31, 2012
	Option					Underlying Swap
Payer Swaptions	Cost		Fair Value		Average Months to Expiration	Notional Amount		Average Fixed Pay Rate		Average Receive Rate	Average Term (Years)
One year or less	$	76	$	15	4	$	5,150	2.65	%	1M / 3M LIBOR	8.6
Greater than 1 year and less than/equal to 2 years	65		34		19	4,050		2.82	%	3M LIBOR	6.7
Greater than 2 years and less than/equal to 3 years	97		87		33	3,900		3.51	%	3M LIBOR	8.6
Greater than 3 years and less than/equal to 4 years	12		11		46	450		3.20	%	3M LIBOR	6.1
Greater than 4 years and less than/equal to 5 years	24		24		59	900		3.33	%	3M LIBOR	5.0
Total/Wtd Avg	$	274	$	171	21	$	14,450	2.99	%	1M / 3M LIBOR	7.8

The following table summarizes our contracts to purchase and sell TBA and specified agency securities on a forward basis as of March 31, 2013 and December 31, 2012 (in millions):



	March 31, 2013												December 31, 2012
Purchase and Sale Contracts for TBAs and Forward Settling Securities	Notional Amount ⁽¹⁾			Cost Basis ⁽²⁾			Market Value ⁽³⁾			Net Carrying Value ⁽⁴⁾			Notional Amount ⁽¹⁾			Cost Basis ⁽²⁾			Market Value ⁽³⁾			Net Carrying Value ⁽⁴⁾
TBA securities:
Purchase contracts	$	29,144		$	30,170		$	30,161		$	(9	)	$	21,705		$	22,603		$	22,719		$	116
Sale contracts	(2,926		)	(2,928		)	(2,930		)	(2		)	(9,378		)	(9,991		)	(10,011		)	(20		)
TBA securities, net ⁽⁵⁾	26,218			27,242			27,231			(11		)	12,327			12,612			12,708			96
Forward settling securities:
Purchase contracts	50			52			52			—			150			163			162			(1		)
Forward settling securities, net ⁽⁶⁾	50			52			52			—			150			163			162			(1		)
Total TBA and forward settling securities, net	$	26,268		$	27,294		$	27,283		$	(11	)	$	12,477		$	12,775		$	12,870		$	95

________________________


1.	Notional amount represents the par value (or principal balance) of the underlying agency security.


2.	Cost basis represents the forward price to be paid for the underlying agency security.


3.	Market value represents the current market value of the TBA contract (or of the underlying agency security) as of period-end.


4.	Net carrying value represents the difference between the market value of the TBA contract as of period-end and the cost basis and is reported in derivative assets / (liabilities), at fair value in our consolidated balance sheets.


5.	Includes 15-year and 30-year TBA securities of varying coupons


6.	Includes 30-year fixed securities of varying coupons

Gain (Loss) From Derivative Instruments and Other Securities, Net

The tables below summarize the effect of derivative instruments on our consolidated statements of comprehensive income for the three months ended March 31, 2013 and 2012 (in millions):



	Three Months Ended March 31, 2013
Derivative and Other Hedging Instruments	Notional Amount December 31, 2012		Additions	Settlement, Termination, Expiration or Exercise		Notional Amount March 31, 2013		Amount of Gain/(Loss) Recognized in Income on Derivatives⁽¹⁾
Purchase of TBA and forward settling agency securities	$	21,855	77,600	(70,261	)	$	29,194	$	(185	)
Sale of TBA and forward settling agency securities	$	9,378	34,333	(40,785	)	$	2,926	83
Interest rate swaps	$	46,850	5,750	(1,350	)	$	51,250	54
Payer swaptions	$	14,450	11,150	(2,700	)	$	22,900	(44		)
Short sales of U.S. Treasury securities	$	11,835	9,935	(9,210	)	$	12,560	(3		)
U.S. Treasury futures - short	$	—	800	—		$	800	(15		)
								$	(110	)

________________________________


1.	Excludes a loss of $1 million from interest-only and principal-only securities and a gain of $13 million from debt of consolidated VIEs re-measured at fair value through earnings recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income.



	Three Months Ended March 31, 2012
Derivative and Other Hedging Instruments	Notional Amount December 31, 2011		Additions	Settlement, Termination, Expiration or Exercise		Notional Amount March 31, 2012		Amount of Gain/(Loss) Recognized in Income on Derivatives⁽¹⁾
Purchase of TBA and forward settling agency securities	$	3,699	22,313	(24,225	)	$	1,787	$	67
Sale of TBA and forward settling agency securities	$	3,803	30,829	(25,579	)	$	9,053	(51		)
Interest rate swaps	$	30,250	7,850	—		$	38,100	(44		)
Payer swaptions	$	3,200	7,950	(650	)	$	10,500	3
Short sales of U.S. Treasury securities	$	880	10,990	(8,005	)	$	3,865	52
US Treasury futures - short	$	783	1,653	(783	)	$	1,653	21
Markit IOS total return swaps - long	$	41	—	(2	)	$	39	1
Markit IOS total return swaps - short	$	206	—	(12	)	$	194	(3		)
								$	46

______________________


1.	Excludes a $1 million gain on interest-only and principal-only securities re-measured at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income.

Credit Risk-Related Contingent Features

The use of derivatives creates exposure to credit risk relating to potential losses that could be recognized in the event that the counterparties to these instruments fail to perform their obligations under the contracts. We minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings and monitoring positions with individual counterparties. In addition, we may be required to pledge assets as collateral for our derivatives, whose amounts vary over time based on the market value, notional amount and remaining term of the derivative contract. In the event of a default by a counterparty we may not receive payments provided for under the terms of our derivative agreements, and may have difficulty obtaining our assets pledged as collateral for our derivatives. The cash and cash equivalents and agency securities pledged as collateral for our derivative instruments is included in restricted cash and agency securities, respectively, on our consolidated balance sheets.

Each of our International Swaps and Derivatives Association ("ISDA") Master Agreements contains provisions under which we are required to fully collateralize our obligations under the swap instrument if at any point the fair value of the swap represents a liability greater than the minimum transfer amount contained within our agreements. We were also required to post initial collateral upon execution of certain of our swap transactions. If we breach any of these provisions, we will be required to settle our obligations under the agreements at their termination values.

Further, each of our ISDA Master Agreements also contains a cross default provision under which a default under certain of our other indebtedness in excess of a certain threshold causes an event of default under the agreement. Threshold amounts vary by lender. Following an event of default, we could be required to settle our obligations under the agreements at their termination values. Additionally, under certain of our ISDA Master Agreements, we could be required to settle our obligations under the agreements at their termination values if we fail to maintain certain minimum shareholders’ equity thresholds or our REIT status or if we fail to comply with limits on our leverage above certain specified levels.

As of March 31, 2013, the fair value and termination value of our interest rate swaps in a liability position related to these agreements was $1.1 billion. We had agency securities with fair values of $812 million and restricted cash of $116 million pledged as collateral against our interest rate swap agreements.

- Definition

The entire disclosure for the entity's entire derivative instruments and hedging activities. Describes an entity's risk management strategies, derivatives in hedging activities and non-hedging derivative instruments, the assets, obligations, liabilities, revenues and expenses arising therefrom, and the amounts of and methodologies and assumptions used in determining the amounts of such items.

+ References

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+ Details

Fair Value Measurements

3 Months Ended

Mar. 31, 2013

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Fair Value Disclosures [Text Block]

Fair Value Measurements

We determine the fair value of our agency securities and debt of consolidated VIEs based upon fair value estimates obtained from multiple third party pricing services and dealers. In determining fair value, third party pricing sources use various valuation approaches, including market and income approaches. Factors used by third party sources in estimating the fair value of an instrument may include observable inputs such as coupons, primary and secondary mortgage rates, pricing information, credit data, volatility statistics, and other market data that are current as of the measurement date. The availability of observable inputs can vary by instrument and is affected by a wide variety of factors, including the type of instrument, whether the instrument is new and not yet established in the marketplace and other characteristics particular to the instrument. Third party pricing sources may also use certain unobservable inputs, such as assumptions of future levels of prepayment, defaults and foreclosures, especially when estimating fair values for securities with lower levels of recent trading activity. We make inquiries of third party pricing sources to understand the significant inputs and assumptions they used to determine their prices. For further information regarding valuation of our derivative instruments, please refer to the discussion of derivative and other hedging instruments in Note 3.

We review the various third party fair value estimates and perform procedures to validate their reasonableness, including an analysis of the range of third party estimates for each position, comparison to recent trade activity for similar securities, and management review for consistency with market conditions observed as of the measurement date. While we do not adjust prices we obtain from third party pricing sources, we will exclude third party prices for securities from our determination of fair value if we determine (based on our validation procedures and our market knowledge and expertise) that the price is significantly different than observable market data would indicate and we cannot obtain an understanding from the third party source as to the significant inputs used to determine the price.

The validation procedures described above also influence our determination of the appropriate fair value measurement classification. We utilize a three-level valuation hierarchy for disclosure of fair value measurement. The valuation hierarchy is based upon the transparency of inputs to the valuation of an asset or liability as of the measurement date. A financial instrument's categorization within the hierarchy is based upon the lowest level of input that is significant to the fair value measurement. There were no transfers between hierarchy levels during the three months ended March 31, 2013. The three levels of hierarchy are defined as follows:


•	Level 1 Inputs —Quoted prices (unadjusted) for identical unrestricted assets and liabilities in active markets that are accessible at the measurement date.


•	Level 2 Inputs —Quoted prices for similar assets and liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations whose inputs are observable or whose significant value drivers are observable.


•	Level 3 Inputs —Instruments with primarily unobservable market data that cannot be corroborated.

The following table provides a summary of our assets and liabilities that are measured at fair value on a recurring basis as of March 31, 2013 and December 31, 2012 (dollars in millions):



	Fair Value Hierarchy
	Level 1		Level 2		Level 3
March 31, 2013
Assets:
Agency securities	$	—	$	76,295	$	—
Interest rate swaps	—		56		—
Payer swaptions	—		332		—
Other derivative instruments	—		92		—
Total	$	—	$	76,775	$	—
Liabilities:
Debt of consolidated VIEs	$	—	$	862	$	—
Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	12,548		—		—
Interest rate swaps	—		1,100		—
Other derivative instruments	—		117		—
Total	$	12,548	$	2,079	$	—

December 31, 2012
Assets:
Agency securities	$	—	$	85,245	$	—
Interest rate swaps	—		14		—
Payer swaptions	—		171		—
Other derivative instruments	—		116		—
Total	$	—	$	85,546	$	—
Liabilities:
Debt of consolidated VIEs	$	—	$	937	$	—
Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	11,763		—		—
Interest rate swaps	—		1,243		—
Other derivative instruments	—		21		—
Total	$	11,763	$	2,201	$	—

We elected the option to account for debt of consolidated VIEs at fair value with changes in fair value reflected in earnings during the period in which they occur, because we believe this election more appropriately reflects our financial position as both the consolidated agency securities and consolidated debt are presented in a consistent manner, at fair value, on our consolidated balance sheets. We estimate the fair value of the consolidated debt based on a market approach using Level 2 inputs from third-party pricing services and dealer quotes.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 12: http://www.xbrl.org/2003/role/presentationRef
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Reference 13: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Stockholders' Equity

3 Months Ended

Mar. 31, 2013

Stockholders' Equity Note [Abstract]

Stockholders' Equity

Follow-On Equity Offering

In March 2013, we completed a public offering in which 57.5 million shares of our common stock were sold to the underwriters at a price of $31.34 per share. Upon completion of the March offering, we received proceeds, net of offering expenses, of approximately $1.8 billion. The underwriters in the offering sold the shares of our common stock in one or more transactions on the NASDAQ Global Select Market, in the over-the-counter market, through negotiated transactions or otherwise at market prices prevailing at the time of sale.

At-the-Market Offering Program

We have entered into sales agreements with sales agents to publicly offer and sell shares of our common stock in privately negotiated and/or at-the-market transactions from time to time. During the three months ended March 31, 2013, we had no sales under this program. As of March 31, 2013, 16.7 million shares remain available for issuance under these sales agreements. The sales agreements will remain in effect until all of the shares are sold under the agreements, subject to early termination rights.

Dividend Reinvestment and Direct Stock Purchase Plan

We sponsor a dividend reinvestment and direct stock purchase plan through which stockholders may purchase additional shares of our common stock by reinvesting some or all of the cash dividends received on shares of our common stock. Stockholders may also make optional cash purchases of shares of our common stock subject to certain limitations detailed in the plan prospectus. During the three months ended March 31, 2013, there were no shares issued under the plan. As of March 31, 2013, 4.7 million shares remain under the plan.

Stock Repurchase Program

In October 2012, our Board of Directors adopted a program that may provide for stock repurchases of up to $500 million of our outstanding shares of common stock through December 31, 2013. Shares of our common stock may be purchased in the open market, including through block purchases, or through privately negotiated transactions, or pursuant to any trading plan that may be adopted in accordance with Rule 10b5-1 of the Securities and Exchange Commission. The timing, manner, price and amount of any repurchases will be determined at our discretion and the program may be suspended, terminated or modified at any time for any reason. We intend to repurchase shares only when the purchase price is less than our estimate of our current net asset value per share of our common stock. Generally, when we repurchase our common stock at a discount to our net asset value, the net asset value of our remaining shares of common stock outstanding increases. In addition, we do not intend to repurchase any shares from directors, officers or other affiliates. The program does not obligate us to acquire any specific number of shares, and all repurchases will be made in accordance with SEC Rule 10b-18, which sets certain restrictions on the method, timing, price and volume of stock repurchases. During the three months ended March 31, 2013, we had no stock repurchases under the program. As of March 31, 2013, we have $423 million remaining available for stock repurchases under the program.

Accumulated Other Comprehensive Income (Loss)

The following table summarizes changes to accumulated OCI for the three months ended March 31, 2013 (in millions):



	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated OCI Balance
Balance as of December 31, 2012	$	2,041		$	(486	)	$	1,555
OCI before reclassifications	(863		)	—			(863		)
Amounts reclassified from accumulated OCI	26			49			75
Net current period OCI	(837		)	49			(788		)
Balance as of March 31, 2013	$	1,204		$	(437	)	$	767

The following table summarizes reclassifications out of accumulated OCI for the three months ended March 31, 2013 (in millions):

- Definition

The entire disclosure for shareholders' equity, comprised of portions attributable to the parent entity and noncontrolling interest, if any, including other comprehensive income (as applicable). Including, but not limited to: (1) balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings; (2) accumulated balance for each classification of other comprehensive income and total amount of comprehensive income; (3) amount and nature of changes in separate accounts, including the number of shares authorized and outstanding, number of shares issued upon exercise and conversion, and for other comprehensive income, the adjustments for reclassifications to net income; (4) rights and privileges of each class of stock authorized; (5) basis of treasury stock, if other than cost, and amounts paid and accounting treatment for treasury stock purchased significantly in excess of market; (6) dividends paid or payable per share and in the aggregate for each class of stock for each period presented; (7) dividend restrictions and accumulated preferred dividends in arrears (in aggregate and per share amount); (8) retained earnings appropriations or restrictions, such as dividend restrictions; (9) impact of change in accounting principle, initial adoption of new accounting principle and correction of an error in previously issued financial statements; (10) shares held in trust for Employee Stock Ownership Plan (ESOP); (11) deferred compensation related to issuance of capital stock; (12) note received for issuance of stock; (13) unamortized discount on shares; (14) description, terms, and number of warrants or rights outstanding; (15) shares under subscription and subscription receivables, effective date of new retained earnings after quasi-reorganization and deficit eliminated by quasi-reorganization and, for a period of at least ten years after the effective date, the point in time from which the new retained dates; and (16) retroactive effective of subsequent change in capital structure.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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+ Details

Offsetting Assets and Liabilities (Notes)

3 Months Ended

Mar. 31, 2013

Offsetting Assets and Liabilities [Abstract]

Offsetting Assets and Liabilities [Text Block]

Offsetting Assets and Liabilities

Certain of our repurchase agreements and derivative transactions are governed by underlying agreements that generally provide for a right of setoff under master netting arrangements (or similar agreements), including in the event of default or in the event of bankruptcy of either party to the transactions. We present our assets and liabilities subject to such arrangements on a gross basis in our consolidated balance sheets. The following tables present information about our assets and liabilities that are subject to such arrangements and can potentially be offset on our consolidated balance sheets as of March 31, 2013 and December 31, 2012 (in millions):

Offsetting of Financial Assets and Derivative Assets:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Assets		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Assets Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Received ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	388	$	—	$	388	$	(388	)	$	—		$	—
Receivable under reverse repurchase agreements	12,291		—		12,291		(10,973		)	(1,231		)	87
Total derivative, other hedging instruments and other assets	$	12,679	$	—	$	12,679	$	(11,361	)	$	(1,231	)	$	87

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	185	$	—	$	185	$	(185	)	$	—		$	—
Receivable under reverse repurchase agreements	11,818		—		11,818		(10,482		)	(1,157		)	179
Total derivative, other hedging instruments and other assets	$	12,003	$	—	$	12,003	$	(10,667	)	$	(1,157	)	$	179

Offsetting of Financial Liabilities and Derivative Liabilities:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Pledged ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	1,100	$	—	$	1,100	$	(388	)	$	(705	)	$	7
Repurchase agreements	66,260		—		66,260		(10,973		)	(55,287		)	—
Total derivative, other hedging instruments and other liabilities	$	67,360	$	—	$	67,360	$	(11,361	)	$	(55,992	)	$	7

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	1,243	$	—	$	1,243	$	(185	)	$	(1,058	)	$	—
Repurchase agreements	74,478		—		74,478		(10,482		)	(63,996		)	—
Total derivative, other hedging instruments and other liabilities	$	75,721	$	—	$	75,721	$	(10,667	)	$	(65,054	)	$	—

_______________________


1.	Reported under derivative assets / liabilities, at fair value in the accompanying consolidated balance sheets. Refer to Note 6 for a reconciliation of derivative assets / liabilities, at fair value to their sub-components.


2.	Includes cash and securities received / pledged as collateral, at fair value. Amounts presented are limited to collateral pledged sufficient to reduce the net amount to zero for individual counterparties, as applicable. Refer to Note 4 for additional information regarding assets pledged as collateral.

Offsetting Assets and Liabilities [Table Text Block]

The following tables present information about our assets and liabilities that are subject to such arrangements and can potentially be offset on our consolidated balance sheets as of March 31, 2013 and December 31, 2012 (in millions):

Offsetting of Financial Assets and Derivative Assets:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Assets		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Assets Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Received ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	388	$	—	$	388	$	(388	)	$	—		$	—
Receivable under reverse repurchase agreements	12,291		—		12,291		(10,973		)	(1,231		)	87
Total derivative, other hedging instruments and other assets	$	12,679	$	—	$	12,679	$	(11,361	)	$	(1,231	)	$	87

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	185	$	—	$	185	$	(185	)	$	—		$	—
Receivable under reverse repurchase agreements	11,818		—		11,818		(10,482		)	(1,157		)	179
Total derivative, other hedging instruments and other assets	$	12,003	$	—	$	12,003	$	(10,667	)	$	(1,157	)	$	179

Offsetting of Financial Liabilities and Derivative Liabilities:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Pledged ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	1,100	$	—	$	1,100	$	(388	)	$	(705	)	$	7
Repurchase agreements	66,260		—		66,260		(10,973		)	(55,287		)	—
Total derivative, other hedging instruments and other liabilities	$	67,360	$	—	$	67,360	$	(11,361	)	$	(55,992	)	$	7

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	1,243	$	—	$	1,243	$	(185	)	$	(1,058	)	$	—
Repurchase agreements	74,478		—		74,478		(10,482		)	(63,996		)	—
Total derivative, other hedging instruments and other liabilities	$	75,721	$	—	$	75,721	$	(10,667	)	$	(65,054	)	$	—

_______________________


1.	Reported under derivative assets / liabilities, at fair value in the accompanying consolidated balance sheets. Refer to Note 6 for a reconciliation of derivative assets / liabilities, at fair value to their sub-components.


2.	Includes cash and securities received / pledged as collateral, at fair value. Amounts presented are limited to collateral pledged sufficient to reduce the net amount to zero for individual counterparties, as applicable. Refer to Note 4 for additional information regarding assets pledged as collateral.

Summary of Significant Accounting Policies (Policy)	3 Months Ended
Summary of Significant Accounting Policies (Policy)	Mar. 31, 2013
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investment Securities	Investment Securities ASC Topic 320, Investments—Debt and Equity Securities (“ASC 320”), requires that at the time of purchase, we designate a security as held-to-maturity, available-for-sale or trading, depending on our ability and intent to hold such security to maturity. Securities classified as trading and available-for-sale are reported at fair value, while securities classified as held-to-maturity are reported at amortized cost. We may, from time to time, sell any of our investment securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our investment securities as available-for-sale. All securities classified as available-for-sale are reported at fair value, with unrealized gains and losses reported in accumulated other comprehensive income ("OCI"), a separate component of stockholders’ equity. Upon the sale of a security, we determine the cost of the security and the amount of unrealized gains or losses to reclassify out of accumulated OCI into earnings based on the specific identification method. Interest-only securities and inverse interest-only securities (collectively referred to as “interest-only securities”) represent our right to receive a specified proportion of the contractual interest flows of specific agency CMO securities. Principal-only securities represent our right to receive the contractual principal flows of specific agency CMO securities. Interest-only and principal-only securities are measured at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Our investments in interest-only and principal-only securities are included in agency MBS securities, at fair value on the accompanying consolidated balance sheets. We estimate the fair value of our investment securities based on a market approach using Level 2 inputs from third-party pricing services and non-binding dealer quotes derived from common market pricing methods. Such methods incorporate, but are not limited to, reported trades and executable bid and asked prices for similar securities, bench mark interest rate curves, such as the spread to the U.S. Treasury rate and interest rate swap curves, convexity, duration and the underlying characteristics of the particular security, including coupon, periodic and life caps, rate reset period, issuer, additional credit support and expected life of the security. Refer to Note 8 for further discussion of fair value measurements. We evaluate securities for other-than-temporary impairment (“OTTI”) on at least a quarterly basis, and more frequently when economic or market conditions warrant such evaluation. The determination of whether a security is other-than-temporarily impaired involves judgments and assumptions based on subjective and objective factors. When an investment security is impaired, an OTTI is considered to have occurred if (i) we intend to sell the investment security (i.e. a decision has been made as of the reporting date) or (ii) it is more likely than not that we will be required to sell the investment security before recovery of its amortized cost basis. If we intend to sell the security or if it is more likely than not that we will be required to sell the investment security before recovery of its amortized cost basis, the entire amount of the impairment loss, if any, is recognized in earnings as a realized loss and the cost basis of the security is adjusted to its fair value. We did not recognize any OTTI charges on our investment securities for the three months ended March 31, 2013 and 2012.
Interest Income	Interest Income Interest income is accrued based on the outstanding principal amount of the investment securities and their contractual terms. Premiums and discounts associated with the purchase of investment securities are amortized or accreted into interest income over the projected lives of the securities, including contractual payments and estimated prepayments using the interest method in accordance with ASC Subtopic 310-20, Receivables—Nonrefundable Fees and Other Costs (“ASC 310-20”). We estimate long-term prepayment speeds of our agency securities using a third-party service and market data. The third-party service estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates and mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, volatility and other factors. We review the prepayment speeds estimated by the third-party service and compare the results to market consensus prepayment speeds, if available. We also consider historical prepayment speeds and current market conditions to validate the reasonableness of the prepayment speeds estimated by the third-party service and, based on our Manager’s judgment, we may make adjustments to their estimates. Actual and anticipated prepayment experience is reviewed quarterly and effective yields are recalculated when differences arise between (i) our previously estimated future prepayments and (ii) actual prepayments to date plus current estimated future prepayments. If the actual and estimated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. The yield on our adjustable rate securities further assumes that the securities reset at a rate equal to the underlying index rate in effect as of the date we acquired the security plus the stated margin.
Derivative and other Hedging Instruments	Derivative Instruments We use a variety of derivative instruments to economically hedge a portion of our exposure to market risks, including interest rate risk, prepayment risk and extension risk. The objective of our risk management strategy is to reduce fluctuations in net book value over a range of interest rate scenarios. In particular, we attempt to mitigate the risk of the cost of our variable rate liabilities increasing during a period of rising interest rates. The principal instruments that we use are interest rate swaps and options to enter into interest rate swaps (“interest rate swaptions”). We also utilize forward contracts for the purchase or sale of agency MBS securities on a generic pool, or to-be-announced, basis ("TBA contracts") and on a non-generic specified pool basis, and we utilize U.S. Treasury securities and U.S. Treasury futures contracts, primarily through short sales. We may also purchase or write put or call options on TBA securities and we may invest in other types of mortgage derivatives, such as interest-only securities, and synthetic total return swaps, such as the Markit IOS Synthetic Total Return Swap Index (“Markit IOS Index”). We may also enter into TBA contracts as a means of investing in and financing agency securities. Pursuant to TBA contracts, we agree to purchase, for future delivery, agency securities with certain principal and interest terms and certain types of collateral, but the particular agency securities to be delivered are not identified until shortly before the TBA settlement date. We also may choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting short position (referred to as a "pair off"), net settling the paired off positions for cash, and simultaneously purchasing a similar TBA contract for a later settlement date. This transaction is commonly referred to as a “dollar roll.” The agency securities purchased for a forward settlement date are typically priced at a discount to agency securities for settlement in the current month. This difference (or discount) is referred to as the “price drop.” The price drop is the economic equivalent of net interest carry income on the underlying agency securities over the roll period (interest income less implied financing cost) and is commonly referred to as "dollar roll income." Consequently, forward purchases of agency securities and dollar roll transactions represent a form of off-balance sheet financing. We account for derivative instruments in accordance with ASC Topic 815, Derivatives and Hedging (“ASC 815”). ASC 815 requires an entity to recognize all derivatives as either assets or liabilities in the balance sheet and to measure those instruments at fair value. Our derivative agreements generally contain provisions that allow for netting or setting off derivative assets and liabilities with each counterparty; however, we report related assets and liabilities on a gross basis in our consolidated balance sheets. Derivative instruments in a gain position are reported as derivative assets at fair value and derivative instruments in a loss position are reported as derivative liabilities at fair value in our consolidated balance sheets. Changes in fair value of derivative instruments and periodic settlements related to our derivative instruments are recorded in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Cash receipts and payments related to derivative instruments are classified in our consolidated statements of cash flows according to the underlying nature or purpose of the derivative transaction, generally in the investing section. The use of derivatives creates exposure to credit risk relating to potential losses that could be recognized in the event that the counterparties to these instruments fail to perform their obligations under the contracts. We attempt to minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to economically hedge the variable cash flows associated with borrowings made under our repurchase agreement facilities. Under our interest rate swap agreements, we typically pay a fixed rate and receive a floating rate based on one, three or six-month LIBOR ("payer swap") with terms up to 10 years, which has the effect of modifying the repricing characteristics of our repurchase agreements and cash flows on such liabilities. We estimate the fair value of interest rate swaps using a combination of inputs from counterparty and third-party pricing models to estimate the net present value of the future cash flows using a forward interest rate yield curve in effect as of the end of the measurement period. We also incorporate both our own and our counterparties’ nonperformance risk in estimating the fair value of our interest rate swaps. In considering the effect of nonperformance risk, we consider the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We purchase interest rate swaptions to help mitigate the potential impact of larger increases or decreases in interest rates on the performance of our investment portfolio (referred to as “convexity risk”). The interest rate swaptions provide us the option to enter into an interest rate swap agreement for a predetermined notional amount, stated term and pay and receive interest rates in the future. Our swaption agreements typically provide us the option to enter into a pay fixed rate interest rate swap, which we refer as “payer swaptions”. We may also enter into swaption agreements that provide us the option to enter into a receive fixed interest rate swap, which we refer to as "receiver swaptions". The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. The premium is valued at an amount equal to the fair value of the swaption that would have the effect of closing the position adjusted for nonperformance risk, if any. The difference between the premium and the fair value of the swaption is reported in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income. If a swaption expires unexercised, the realized loss on the swaption would be equal to the premium paid. If we sell or exercise a swaption, the realized gain or loss on the swaption would be equal to the difference between the cash or the fair value of the underlying interest rate swap received and the premium paid. We estimate the fair value of interest rate swaptions using a combination of inputs from counterparty and third-party pricing models based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option, adjusted for non-performance risk, if any. TBA securities A TBA security is a forward contract for the purchase ("long position") or sale ("short position") of agency MBS at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific agency MBS delivered into the contract upon the settlement date, published each month by the Securities Industry and Financial Markets Association, are not known at the time of the transaction. We enter into TBA contracts as a means of hedging against short-term changes in interest rates. We may also enter into TBA contracts as a means of acquiring agency securities and we may from time to time utilize TBA dollar roll transactions to finance agency MBS purchases. We account for TBA contracts as derivative instruments since we cannot assert that it is probable at inception and throughout the term of the TBA contract that we will take physical delivery of the agency security upon settlement of the contract. We account for TBA dollar roll transactions as a series of derivative transactions. Gains, losses and dollar roll income associated with our TBA contracts and dollar roll transactions are recognized in our consolidated statements of comprehensive income in gain (loss) on derivative instruments and other securities, net. We estimate the fair value of TBA securities based on similar methods used to value our agency MBS securities. Forward commitments to purchase or sell specified agency MBS We enter into forward commitments to purchase or sell specified agency MBS from time to time as a means of acquiring assets or as a hedge against short-term changes in interest rates. We account for contracts for the purchase or sale of specified agency MBS securities as derivatives if the delivery of the specified agency MBS and settlement extends beyond the shortest period possible for that type of security. Realized and unrealized gains and losses associated with forward commitments accounted for as derivatives are recognized in our consolidated statements of comprehensive income in gain (loss) on derivative instruments and other securities, net. We estimate the fair value of forward commitments to purchase or sell specified agency MBS based on similar methods used to value agency MBS, as well as the remaining length of time of the forward commitment. U.S. Treasury securities We purchase or sell short U.S. Treasury securities and U.S. Treasury futures contracts to help mitigate the potential impact of changes in interest rates on the performance of our portfolio. We borrow securities to cover short sales of U.S. Treasury securities under reverse repurchase agreements. We account for these as securities borrowing transactions and recognize an obligation to return the borrowed securities at fair value on the balance sheet based on the value of the underlying borrowed securities as of the reporting date. Gains and losses associated with purchases and short sales of U.S. Treasury securities are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative and other Hedging Instruments	Discontinuation of hedge accounting for interest rate swap agreements Prior to the third quarter of 2011, we entered into interest rate swap agreements typically with the intention of qualifying for hedge accounting under ASC 815. However, as of September 30, 2011, we elected to discontinue hedge accounting for our interest rate swaps. Upon discontinuation of hedge accounting, the net deferred loss related to our de-designated interest rate swaps remained in accumulated OCI and is being reclassified from accumulated OCI into interest expense on a straight-line basis over the remaining term of each interest rate swap.

- Definition

Disclosure of accounting policy for its derivative instruments and hedging activities.

+ References

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-Paragraph n
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+ Details

- Definition

Disclosure of accounting policy for investments in financial assets, including marketable securities (debt and equity securities with readily determinable fair values), investments accounted for under the equity method and cost method, securities borrowed and loaned, and repurchase and resale agreements. For marketable securities, the disclosure may include the entity's accounting treatment for transfers between investment categories and how the fair values for such securities are determined. Also, for all investments, an entity may describe its policy for assessing, recognizing and measuring impairment of the investment.

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+ Details

Investment Securities (Tables)

3 Months Ended

Mar. 31, 2013

Available-for-sale Securities [Abstract]

Agency Securities [Table Text Block]

The following tables summarize our investments in agency MBS as of March 31, 2013 (dollars in millions):



	March 31, 2013
Agency MBS	Fannie Mae			Freddie Mac			Ginnie Mae			Total
Available-for-sale agency MBS:
Agency MBS, par	$	50,510		$	20,228		$	218		$	70,956
Unamortized discount	(20		)	—			—			(20		)
Unamortized premium	2,691			939			9			3,639
Amortized cost	53,181			21,167			227			74,575
Gross unrealized gains	1,044			330			6			1,380
Gross unrealized losses	(116		)	(60		)	—			(176		)
Total available-for-sale agency MBS, at fair value	54,109			21,437			233			75,779
Agency MBS remeasured at fair value through earnings:
Interest-only and principal-only strips, amortized cost ⁽¹⁾	463			50			—			513
Gross unrealized gains	24			1			—			25
Gross unrealized losses	(11		)	(11		)	—			(22		)
Total agency MBS remeasured at fair value through earnings	476			40			—			516
Total agency MBS, at fair value	$	54,585		$	21,477		$	233		$	76,295
Weighted average coupon as of March 31, 2013⁽²⁾	3.75		%	3.67		%	3.76		%	3.73		%
Weighted average yield as of March 31, 2013⁽³⁾	2.74		%	2.80		%	1.59		%	2.75		%
Weighted average yield for the three months ended March 31, 2013⁽³⁾	2.79		%	2.83		%	1.56		%	2.80		%

________________________


1.	The underlying unamortized principal balance (“UPB” or “par value”) of our interest-only agency MBS strips was $1.5 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of March 31, 2013. The par value of our principal-only agency MBS strips was $295 million as of March 31, 2013.


2.	The weighted average coupon includes the interest cash flows from our interest-only agency MBS strips taken together with the interest cash flows from our fixed-rate, adjustable-rate and CMO agency MBS as a percentage of the par value of our agency MBS (excluding the UPB of our interest-only securities) as of March 31, 2013.


3.	Incorporates a weighted average future constant prepayment rate assumption of 9% based on forward rates as of March 31, 2013

The following tables summarize our investments in agency MBS as of December 31, 2012 (dollars in millions):



	December 31, 2012
Agency MBS	Fannie Mae			Freddie Mac			Ginnie Mae			Total
Available-for-sale agency MBS:
Agency MBS, par	$	58,912		$	19,336		$	238		$	78,486
Unamortized premium	3,208			948			10			4,166
Amortized cost	62,120			20,284			248			82,652
Gross unrealized gains	1,585			481			6			2,072
Gross unrealized losses	(18		)	(7		)	—			(25		)
Available-for-sale agency MBS, at fair value	63,687			20,758			254			84,699
Agency MBS remeasured at fair value through earnings:
Interest-only and principal-only strips, amortized cost ⁽¹⁾	486			55			—			541
Gross unrealized gains	26			1			—			27
Gross unrealized losses	(9		)	(13		)	—			(22		)
Agency MBS remeasured at fair value through earnings	503			43			—			546
Total agency MBS, at fair value	$	64,190		$	20,801		$	254		$	85,245
Weighted average coupon as of December 31, 2012 ⁽²⁾	3.70		%	3.67		%	3.77		%	3.69		%
Weighted average yield as of December 31, 2012 ⁽³⁾	2.62		%	2.61		%	1.60		%	2.61		%
Weighted average yield for the year ended December 31, 2012 ⁽³⁾	2.83		%	2.83		%	1.63		%	2.82		%

________________________


1.	The UPB of our interest-only securities was $1.7 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of December 31, 2012. The par value of our principal-only agency MBS strips was $302 million as of December 31, 2012.


2.	The weighted average coupon includes the interest cash flows from our interest-only securities taken together with the interest cash flows from our fixed-rate, adjustable-rate and CMO securities as a percentage of the par value of our agency securities (excluding the UPB of our interest-only securities) as of December 31, 2012.


3.	Incorporates a weighted average future constant prepayment rate assumption of 11% based on forward rates as of December 31, 2012.



	December 31, 2012
Agency MBS	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Fixed-Rate	$	81,617	$	2,043	$	(25	)	$	83,635
Adjustable-Rate	865		26		—			891
CMO	170		3		—			173
Interest-only strips	541		27		(22		)	546
Total agency MBS	$	83,193	$	2,099	$	(47	)	$	85,245

Summary Of Agency Securities Estimated Weighted Average Life Classifications



	March 31, 2013								December 31, 2012
Estimated Weighted Average Life of Agency MBS Classified as Available-for-Sale ⁽¹⁾	Fair Value		Amortized Cost		Weighted Average Coupon		Weighted Average Yield		Fair Value		Amortized Cost		Weighted Average Coupon		Weighted Average Yield
≤ 3 years	279		272		4.54	%	3.01	%	1,119		1,108		4.18	%	2.14	%
> 3 years and ≤ 5 years	17,428		16,835		3.76	%	2.67	%	27,448		26,750		3.36	%	2.29	%
> 5 years and ≤10 years	49,750		49,132		3.68	%	2.76	%	54,054		52,735		3.69	%	2.75	%
> 10 years	8,322		8,336		2.96	%	2.65	%	2,078		2,059		3.44	%	2.65	%
Total	$	75,779	$	74,575	3.62	%	2.73	%	$	84,699	$	82,652	3.59	%	2.59	%

_______________________


1.	Excludes interest and principal-only strips.

Summary Of Agency Securities Pledged As Collateral Under Repurchase Agreements by Remaining Maturity



	March 31, 2013						December 31, 2012
Securities Pledged by Remaining Maturity of Repurchase Agreements and Debt of Consolidated VIEs	Fair Value of Pledged Securities		Amortized Cost of Pledged Securities		Accrued Interest on Pledged Securities		Fair Value of Pledged Securities		Amortized Cost of Pledged Securities		Accrued Interest on Pledged Securities
Agency MBS:
Less than 30 days	$	28,076	$	27,572	$	80	$	29,284	$	28,525	$	82
31 - 59 days	14,020		13,774		39		21,716		21,251		58
60 - 90 days	7,321		7,241		21		16,188		15,780		45
Greater than 90 days	21,541		21,220		60		12,747		12,447		37
Total agency MBS	$	70,958	$	69,807	$	200	$	79,935	$	78,003	$	222

Schedule of Investments Owned and Pledged as Collateral [Table Text Block]



	March 31, 2013
Assets Pledged	Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements		Total
Agency MBS - fair value	$	69,537	$	1,421	$	812	$	229	$	71,999
Accrued interest on pledged securities	196		4		2				202
Restricted cash	—		—		116		383		499
Total	$	69,733	$	1,425	$	930	$	612	$	72,700



	December 31, 2012
Assets Pledged	Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements		Total
Agency MBS - fair value	$	78,400	$	1,535	$	1,065	$	501	$	81,501
Accrued interest on pledged securities	217		5		3		1		226
Restricted cash	—		—		249		150		399
Total	$	78,617	$	1,540	$	1,317	$	652	$	82,126

Summary of Changes in Accumulated OCI for Agency Securitie [Table Text Block]

The following table summarizes changes in accumulated OCI, a separate component of stockholders equity, for our available-for-sale securities for the three months ended March 31, 2013 and 2012 (in millions):



Agency Securities Classified as Available-for-Sale	Beginning Accumulated OCI Balance		Unrealized Gains and (Losses), Net		Reversal of Prior Period Unrealized (Gains) and Losses, Net on Realization		Ending Accumulated OCI Balance
Three months ended March 31, 2013	$	2,041	(863	)	26		$	1,204
Three months ended March 31, 2012	$	1,002	110		(216	)	$	896

Components of Investment Securities [Table Text Block]



	March 31, 2013
Agency MBS	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Fixed-Rate	$	73,649	$	1,355	$	(176	)	$	74,828
Adjustable-Rate	773		21		—			794
CMO	153		4		—			157
Interest-only and principal-only strips	513		25		(22		)	516
Total agency MBS	$	75,088	$	1,405	$	(198	)	$	76,295



	December 31, 2012
Agency MBS	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss			Fair Value
Fixed-Rate	$	81,617	$	2,043	$	(25	)	$	83,635
Adjustable-Rate	865		26		—			891
CMO	170		3		—			173
Interest-only strips	541		27		(22		)	546
Total agency MBS	$	83,193	$	2,099	$	(47	)	$	85,245

Summary of Continuous Unrealized Loss Position of Available for Sale Securities [Table Text Block]



	Unrealized Loss Position For
	Less than 12 Months					12 Months or More					Total
Agency Securities Classified as Available-for-Sale	Estimated Fair Value		Unrealized Loss			Estimated Fair Value		Unrealized Loss			Estimated Fair Value		Unrealized Loss
March 31, 2013	$	25,963	$	(174	)	$	84	$	(2	)	$	26,047	$	(176	)
December 31, 2012	$	8,430	$	(25	)	$	—	$	—		$	8,430	$	(25	)

Summary of Net Gain from Sale of Agency Securities [Table Text Block]

he following table is a summary of our net (loss) gain from the sale of agency MBS for the three months ended March 31, 2013 and 2012 (in millions):



	Three Months Ended
Agency MBS	March 31, 2013			March 31, 2012
Agency MBS sold, at cost	$	(20,328	)	$	(9,243	)
Proceeds from agency MBS sold ⁽¹⁾	20,302			9,459
Net (loss) gain on sale of agency MBS	$	(26	)	$	216

Gross gain on sale of agency MBS	$	87		$	220
Gross loss on sale of agency MBS	(113		)	(4		)
Net (loss) gain on sale of agency MBS	$	(26	)	$	216

________________________


1.	Proceeds include cash received during the period, plus receivable for agency MBS sold during the period as of period end.

Repurchase Agreements and Other Debt (Tables)

3 Months Ended

Mar. 31, 2013

Disclosure of Repurchase Agreements [Abstract]

Schedule of Borrowings under Repurchase Agreements and Weighted Average Interest Rates [Table Text Block]



	March 31, 2013					December 31, 2012
Original Maturity	Repurchase Agreements		Weighted Average Interest Rate		Weighted Average Days to Maturity	Repurchase Agreements		Weighted Average Interest Rate		Weighted Average Days to Maturity
Agency MBS:
≤ 1 month	$	8,059	0.41	%	13	$	4,011	0.48	%	13
> 1 to ≤ 3 months	29,461		0.42	%	30	28,307		0.49	%	37
> 3 to ≤ 6 months	11,173		0.48	%	68	24,303		0.49	%	63
> 6 to ≤ 9 months	4,436		0.49	%	140	5,222		0.54	%	79
> 9 to ≤ 12 months	8,063		0.58	%	216	7,813		0.58	%	222
> 12 to ≤ 24 months	2,099		0.63	%	469	1,917		0.65	%	564
> 24 to ≤ 36 months	2,767		0.67	%	872	2,803		0.69	%	963
> 36 months	202		0.74	%	1,532	102		0.73	%	1,751
Total agency MBS	$	66,260	0.47	%	118	$	74,478	0.51	%	118

Derivative and Other Hedging Instruments (Tables)

3 Months Ended

Mar. 31, 2013

Derivative [Line Items]

Schedule of Interest Rate Swaption Agreements Outstandin [Table Text Block]

The following tables summarize our interest rate swaption agreements outstanding as of March 31, 2013 and December 31, 2012 (dollars in millions):



	March 31, 2013
	Option					Underlying Swap
Payer Swaptions	Cost		Fair Value		Average Months to Expiration	Notional Amount		Average Fixed Pay Rate		Average Receive Rate	Average Term (Years)
One year or less	$	169	$	91	7	$	12,100	2.49	%	1M / 3M LIBOR	8.4
Greater than 1 year and less than/equal to 2 years	81		52		17	4,200		2.81	%	3M LIBOR	6.8
Greater than 2 years and less than/equal to 3 years	139		137		32	5,000		3.42	%	3M LIBOR	8.5
Greater than 3 years and less than/equal to 4 years	12		13		43	450		3.20	%	3M LIBOR	6.1
Greater than 4 years and less than/equal to 5 years	37		39		57	1,150		3.51	%	3M LIBOR	4.5
Total/Wtd Avg	$	438	$332		17	$	22,900	2.81	%	1M / 3M LIBOR	7.9



	December 31, 2012
	Option					Underlying Swap
Payer Swaptions	Cost		Fair Value		Average Months to Expiration	Notional Amount		Average Fixed Pay Rate		Average Receive Rate	Average Term (Years)
One year or less	$	76	$	15	4	$	5,150	2.65	%	1M / 3M LIBOR	8.6
Greater than 1 year and less than/equal to 2 years	65		34		19	4,050		2.82	%	3M LIBOR	6.7
Greater than 2 years and less than/equal to 3 years	97		87		33	3,900		3.51	%	3M LIBOR	8.6
Greater than 3 years and less than/equal to 4 years	12		11		46	450		3.20	%	3M LIBOR	6.1
Greater than 4 years and less than/equal to 5 years	24		24		59	900		3.33	%	3M LIBOR	5.0
Total/Wtd Avg	$	274	$	171	21	$	14,450	2.99	%	1M / 3M LIBOR	7.8

Summary of Long and Short Position of Derivative Instruments

The following table summarizes our contracts to purchase and sell TBA and specified agency securities on a forward basis as of March 31, 2013 and December 31, 2012 (in millions):



	March 31, 2013												December 31, 2012
Purchase and Sale Contracts for TBAs and Forward Settling Securities	Notional Amount ⁽¹⁾			Cost Basis ⁽²⁾			Market Value ⁽³⁾			Net Carrying Value ⁽⁴⁾			Notional Amount ⁽¹⁾			Cost Basis ⁽²⁾			Market Value ⁽³⁾			Net Carrying Value ⁽⁴⁾
TBA securities:
Purchase contracts	$	29,144		$	30,170		$	30,161		$	(9	)	$	21,705		$	22,603		$	22,719		$	116
Sale contracts	(2,926		)	(2,928		)	(2,930		)	(2		)	(9,378		)	(9,991		)	(10,011		)	(20		)
TBA securities, net ⁽⁵⁾	26,218			27,242			27,231			(11		)	12,327			12,612			12,708			96
Forward settling securities:
Purchase contracts	50			52			52			—			150			163			162			(1		)
Forward settling securities, net ⁽⁶⁾	50			52			52			—			150			163			162			(1		)
Total TBA and forward settling securities, net	$	26,268		$	27,294		$	27,283		$	(11	)	$	12,477		$	12,775		$	12,870		$	95

________________________


1.	Notional amount represents the par value (or principal balance) of the underlying agency security.


2.	Cost basis represents the forward price to be paid for the underlying agency security.


3.	Market value represents the current market value of the TBA contract (or of the underlying agency security) as of period-end.


4.	Net carrying value represents the difference between the market value of the TBA contract as of period-end and the cost basis and is reported in derivative assets / (liabilities), at fair value in our consolidated balance sheets.


5.	Includes 15-year and 30-year TBA securities of varying coupons


6.	Includes 30-year fixed securities of varying coupons

Schedule of Outstanding Derivatives Not Designated as Hedging Instruments [Table Text Block]

The table below summarizes fair value information about our derivative assets and liabilities as of March 31, 2013 and December 31, 2012 (in millions):



Derivatives Instruments	Balance Sheet Location	March 31, 2013			December 31, 2012
Interest rate swaps	Derivative assets, at fair value	$	56		$	14
Payer swaptions	Derivative assets, at fair value	332			171
Purchase of TBA and forward settling agency securities	Derivative assets, at fair value	86			116
Sale of TBA and forward settling agency securities	Derivative assets, at fair value	6			—
		$	480		$	301
Interest rate swaps	Derivative liabilities, at fair value	$	(1,100	)	$	(1,243	)
U.S. Treasury futures - short	Derivative liabilities, at fair value	(14		)	—
Purchase of TBA and forward settling agency securities	Derivative liabilities, at fair value	(95		)	(1		)
Sale of TBA and forward settling agency securities	Derivative liabilities, at fair value	(8		)	(20		)
		$	(1,217	)	$	(1,264	)

Schedule Of Outstanding Not Designated As Hedging Instruments [Table Text Block]

The tables below summarize the effect of derivative instruments on our consolidated statements of comprehensive income for the three months ended March 31, 2013 and 2012 (in millions):



	Three Months Ended March 31, 2013
Derivative and Other Hedging Instruments	Notional Amount December 31, 2012		Additions	Settlement, Termination, Expiration or Exercise		Notional Amount March 31, 2013		Amount of Gain/(Loss) Recognized in Income on Derivatives⁽¹⁾
Purchase of TBA and forward settling agency securities	$	21,855	77,600	(70,261	)	$	29,194	$	(185	)
Sale of TBA and forward settling agency securities	$	9,378	34,333	(40,785	)	$	2,926	83
Interest rate swaps	$	46,850	5,750	(1,350	)	$	51,250	54
Payer swaptions	$	14,450	11,150	(2,700	)	$	22,900	(44		)
Short sales of U.S. Treasury securities	$	11,835	9,935	(9,210	)	$	12,560	(3		)
U.S. Treasury futures - short	$	—	800	—		$	800	(15		)
								$	(110	)

________________________________


1.	Excludes a loss of $1 million from interest-only and principal-only securities and a gain of $13 million from debt of consolidated VIEs re-measured at fair value through earnings recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income.



	Three Months Ended March 31, 2012
Derivative and Other Hedging Instruments	Notional Amount December 31, 2011		Additions	Settlement, Termination, Expiration or Exercise		Notional Amount March 31, 2012		Amount of Gain/(Loss) Recognized in Income on Derivatives⁽¹⁾
Purchase of TBA and forward settling agency securities	$	3,699	22,313	(24,225	)	$	1,787	$	67
Sale of TBA and forward settling agency securities	$	3,803	30,829	(25,579	)	$	9,053	(51		)
Interest rate swaps	$	30,250	7,850	—		$	38,100	(44		)
Payer swaptions	$	3,200	7,950	(650	)	$	10,500	3
Short sales of U.S. Treasury securities	$	880	10,990	(8,005	)	$	3,865	52
US Treasury futures - short	$	783	1,653	(783	)	$	1,653	21
Markit IOS total return swaps - long	$	41	—	(2	)	$	39	1
Markit IOS total return swaps - short	$	206	—	(12	)	$	194	(3		)
								$	46

______________________


1.	Excludes a $1 million gain on interest-only and principal-only securities re-measured at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statement of comprehensive income.

Not Designated as Hedging Instrument [Member]

Derivative [Line Items]

Schedule Of Interest Rate Swap Agreement By Remaining Maturity

The following tables summarize our interest rate swap agreements outstanding as of March 31, 2013 and December 31, 2012 (dollars in millions):



	March 31, 2013
Interest Rate Swaps ⁽¹⁾	Notional Amount		Average Fixed Pay Rate		Average Receive Rate		Net Estimated Fair Value			Average Maturity (Years)
Three years or less	$	14,950	1.29	%	0.25	%	$	(309	)	2.0
Greater than 3 years and less than/equal to 5 years	19,750		1.41	%	0.27	%	(535		)	4.0
Greater than 5 years and less than/equal to 7 years	6,100		1.59	%	0.32	%	(145		)	6.0
Greater than 7 years and less than/equal to 10 years	7,250		1.89	%	0.31	%	(37		)	9.1
Greater than 10 years	3,200		2.17	%	0.28	%	(18		)	10.3
Total Payer Interest Rate Swaps	$	51,250	1.51	%	0.28	%	$	(1,044	)	4.8

________________________


1.	Amounts include forward starting swaps of $5.2 billion ranging up to 6 months from March 31, 2013.



	December 31, 2012
Interest Rate Swaps ⁽¹⁾	Notional Amount		Average Fixed Pay Rate		Average Receive Rate		Net Estimated Fair Value			Average Maturity (Years)
Three years or less	$	14,600	1.23	%	0.26	%	$	(294	)	2.0
Greater than 3 years and less than/equal to 5 years	20,250		1.48	%	0.29	%	(666		)	4.1
Greater than 5 years and less than/equal to 7 years	5,600		1.53	%	0.34	%	(163		)	6.1
Greater than 7 years and less than/equal to 10 years	5,200		1.89	%	0.35	%	(113		)	9.2
Greater than 10 years	1,200		1.79	%	0.31	%	7			10.2
Total Payer Interest Rate Swaps	$	46,850	1.46	%	0.29	%	$	(1,229	)	4.4

________________________


1.	Amounts include forward starting swaps of $1.7 billion ranging up to four months from December 31, 2012.

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2013

Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis

The following table provides a summary of our assets and liabilities that are measured at fair value on a recurring basis as of March 31, 2013 and December 31, 2012 (dollars in millions):



	Fair Value Hierarchy
	Level 1		Level 2		Level 3
March 31, 2013
Assets:
Agency securities	$	—	$	76,295	$	—
Interest rate swaps	—		56		—
Payer swaptions	—		332		—
Other derivative instruments	—		92		—
Total	$	—	$	76,775	$	—
Liabilities:
Debt of consolidated VIEs	$	—	$	862	$	—
Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	12,548		—		—
Interest rate swaps	—		1,100		—
Other derivative instruments	—		117		—
Total	$	12,548	$	2,079	$	—

December 31, 2012
Assets:
Agency securities	$	—	$	85,245	$	—
Interest rate swaps	—		14		—
Payer swaptions	—		171		—
Other derivative instruments	—		116		—
Total	$	—	$	85,546	$	—
Liabilities:
Debt of consolidated VIEs	$	—	$	937	$	—
Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	11,763		—		—
Interest rate swaps	—		1,243		—
Other derivative instruments	—		21		—
Total	$	11,763	$	2,201	$	—

Stockholders' Equity Equity Offerings (Tables)

3 Months Ended

Mar. 31, 2013

Class of Stock [Line Items]

Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]

The following table summarizes changes to accumulated OCI for the three months ended March 31, 2013 (in millions):



	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated OCI Balance
Balance as of December 31, 2012	$	2,041		$	(486	)	$	1,555
OCI before reclassifications	(863		)	—			(863		)
Amounts reclassified from accumulated OCI	26			49			75
Net current period OCI	(837		)	49			(788		)
Balance as of March 31, 2013	$	1,204		$	(437	)	$	767

The following table summarizes reclassifications out of accumulated OCI for the three months ended March 31, 2013 (in millions):

Stockholders' Equity Note Disclosure [Text Block]

Stockholders' Equity

Follow-On Equity Offering

At-the-Market Offering Program

Dividend Reinvestment and Direct Stock Purchase Plan

Stock Repurchase Program

Accumulated Other Comprehensive Income (Loss)

The following table summarizes changes to accumulated OCI for the three months ended March 31, 2013 (in millions):



	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated OCI Balance
Balance as of December 31, 2012	$	2,041		$	(486	)	$	1,555
OCI before reclassifications	(863		)	—			(863		)
Amounts reclassified from accumulated OCI	26			49			75
Net current period OCI	(837		)	49			(788		)
Balance as of March 31, 2013	$	1,204		$	(437	)	$	767

The following table summarizes reclassifications out of accumulated OCI for the three months ended March 31, 2013 (in millions):

- Definition

+ References

+ Details

Offsetting Assets and Liabilities (Tables)

3 Months Ended

Mar. 31, 2013

Offsetting Assets and Liabilities [Abstract]

Offsetting Assets and Liabilities [Table Text Block]

Offsetting of Financial Assets and Derivative Assets:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Assets		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Assets Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Received ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	388	$	—	$	388	$	(388	)	$	—		$	—
Receivable under reverse repurchase agreements	12,291		—		12,291		(10,973		)	(1,231		)	87
Total derivative, other hedging instruments and other assets	$	12,679	$	—	$	12,679	$	(11,361	)	$	(1,231	)	$	87

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	185	$	—	$	185	$	(185	)	$	—		$	—
Receivable under reverse repurchase agreements	11,818		—		11,818		(10,482		)	(1,157		)	179
Total derivative, other hedging instruments and other assets	$	12,003	$	—	$	12,003	$	(10,667	)	$	(1,157	)	$	179

Offsetting of Financial Liabilities and Derivative Liabilities:



							Gross Amounts Not Offset in the Consolidated Balance Sheets
	Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Financial Instruments			Collateral Pledged ⁽²⁾			Net Amount
March 31, 2013
Interest rate swap and swaption agreements, at fair value ⁽¹⁾	$	1,100	$	—	$	1,100	$	(388	)	$	(705	)	$	7
Repurchase agreements	66,260		—		66,260		(10,973		)	(55,287		)	—
Total derivative, other hedging instruments and other liabilities	$	67,360	$	—	$	67,360	$	(11,361	)	$	(55,992	)	$	7

December 31, 2012
Interest rate swap and swaption agreements, at fair value⁽¹⁾	$	1,243	$	—	$	1,243	$	(185	)	$	(1,058	)	$	—
Repurchase agreements	74,478		—		74,478		(10,482		)	(63,996		)	—
Total derivative, other hedging instruments and other liabilities	$	75,721	$	—	$	75,721	$	(10,667	)	$	(65,054	)	$	—

_______________________


1.	Reported under derivative assets / liabilities, at fair value in the accompanying consolidated balance sheets. Refer to Note 6 for a reconciliation of derivative assets / liabilities, at fair value to their sub-components.


2.	Includes cash and securities received / pledged as collateral, at fair value. Amounts presented are limited to collateral pledged sufficient to reduce the net amount to zero for individual counterparties, as applicable. Refer to Note 4 for additional information regarding assets pledged as collateral.

Organization (Details)	3 Months Ended
Organization (Details)	Mar. 31, 2013
Organization [Abstract]
Required distribution of taxable net income on a annual basis	90.00%

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Required Annual Distribution of Taxable Net Income	90.00%
Unrealized (loss) gain on derivative instruments, net	$ 49	$ 52
One Month [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	100.00%
Three Month [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	300.00%
Maximum [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	600.00%
Interest Rate Swap [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivative, Average Remaining Maturity	10 years

- Definition

Net of tax amount, before reclassification adjustments, of the change in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Also includes an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6441202&loc=d3e80720-113993

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624171-113959

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 17, 20
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 121
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 7: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 46
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 8: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 24
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 9: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Investment Securities (Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
Investment Securities (Narrative) (Details) $ in Millions	Mar. 31, 2013 USD ($) years	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($) years
Schedule of Available-for-sale Securities [Line Items]
Future Prepayment Rate Assumption Of Investment Portfolio	9.00%		11.00%
Weighted Average Life of Interest Only Securities \| years	6.0		5.7
Weighted Average Life Of Principal Only Securities \| years	7.0		6.4
Unrealized gain on interest-only and principal-only securities	$ 1	$ (1)
Fair value of CMO securities and interest-only strips	673		$ 719
Securitized CMO Securities	1,200		1,300
CMO and Interest Only, Pricincipal Only Securities, Maximum Loss Exposure	316		343
Fair value of agency securities collaterizing debt issued by securitization trust	1,400		1,500
Principal balance of agency securities collaterizing debt issued by securitization trust	1,300		1,400
Other Long-term Debt	$ 862		$ 937

Investment Securities (Summary of Investment in Agency Security) (Details)
$ in Millions

3 Months Ended

12 Months Ended

Mar. 31, 2013

USD ($)

years

Mar. 31, 2012

USD ($)

Dec. 31, 2012

USD ($)

years

Weighted Average Life Of Principal Only Securities | years

7.0

6.4

Debt Instrument, Face Amount

$ 844

$ 908

Securities Held as Collateral, at Fair Value

1,400

1,500

Securitized CMO Securities

1,200

1,300

Unrealized Gain On Derivative Instrument And Trading Securities

(1)

$ 1

Unamortized premium

3,800

4,400

Amortized cost

74,575

82,652

Total agency MBS, at fair value

$ 76,295

$ 85,245

Weighted average coupon

3.73%

^[1]

3.69%

Weighted average yield

2.75%

^[2]

2.61%

Weighted average yield for the year ended

2.80%

^[2]

2.82%

Unamortized principal balance of interest-only strips

$ 1,500

$ 1,700

Unamortized principal balance of principal-only strips

$ 295

$ 302

Weighted average contractual interest rate of interest only strips

5.78%

Average prepayment rate based on forward rate assumption

9.00%

11.00%

Other Long-term Debt

$ 862

$ 937

Gain Loss on Other Debt

$ 0

Fannie Mae [Member]

Total agency MBS, at fair value

$ 54,585

$ 64,190

Weighted average coupon

3.75%

^[1]

3.70%

Weighted average yield

2.74%

^[2]

2.62%

Weighted average yield for the year ended

2.79%

^[2]

2.83%

Freddie Mac [Member]

Total agency MBS, at fair value

$ 21,477

$ 20,801

Weighted average coupon

3.67%

^[1]

3.67%

Weighted average yield

2.80%

^[2]

2.61%

Weighted average yield for the year ended

2.83%

^[2]

2.83%

Ginnie Mae [Member]

Total agency MBS, at fair value

$ 233

$ 254

Weighted average coupon

3.76%

^[1]

3.77%

Weighted average yield

1.59%

^[2]

1.60%

Weighted average yield for the year ended

1.56%

^[2]

1.63%

Available-for-sale Securities [Member]

Agency MBS, par

$ 70,956

$ 78,486

Unamortized discount

(20)

Unamortized premium

3,639

4,166

Amortized cost

74,575

82,652

Gross unrealized gains

1,380

2,072

Gross unrealized losses

(176)

(25)

Total available-for-sale agency MBS, at fair value

75,779

84,699

Available-for-sale Securities [Member] | Fannie Mae [Member]

Agency MBS, par

50,510

58,912

Unamortized discount

(20)

Unamortized premium

2,691

3,208

Amortized cost

53,181

62,120

Gross unrealized gains

1,044

1,585

Gross unrealized losses

(116)

(18)

Total available-for-sale agency MBS, at fair value

54,109

63,687

Available-for-sale Securities [Member] | Freddie Mac [Member]

Agency MBS, par

20,228

19,336

Unamortized discount

Unamortized premium

939

948

Amortized cost

21,167

20,284

Gross unrealized gains

330

481

Gross unrealized losses

(60)

(7)

Total available-for-sale agency MBS, at fair value

21,437

20,758

Available-for-sale Securities [Member] | Ginnie Mae [Member]

Agency MBS, par

218

238

Unamortized discount

Unamortized premium

Amortized cost

227

248

Gross unrealized gains

Gross unrealized losses

Total available-for-sale agency MBS, at fair value

233

254

Agency MBS remeasured at fair value through earnings [Member]

Interest-only and principal-only strips, amortized cost

513

541

^[3]

Gross unrealized gains

Gross unrealized losses

(22)

Total agency MBS remeasured at fair value through earnings, at fair value

516

546

Agency MBS remeasured at fair value through earnings [Member] | Fannie Mae [Member]

Interest-only and principal-only strips, amortized cost

463

486

Gross unrealized gains

Gross unrealized losses

(11)

(9)

Total agency MBS remeasured at fair value through earnings, at fair value

476

503

Agency MBS remeasured at fair value through earnings [Member] | Freddie Mac [Member]

Interest-only and principal-only strips, amortized cost

Gross unrealized gains

Gross unrealized losses

(11)

(13)

Total agency MBS remeasured at fair value through earnings, at fair value

Agency MBS remeasured at fair value through earnings [Member] | Ginnie Mae [Member]

Interest-only and principal-only strips, amortized cost

Gross unrealized gains

Gross unrealized losses

Total agency MBS remeasured at fair value through earnings, at fair value

$ 0

[1]	The underlying unamortized principal balance (“UPB” or “par value”) of our interest-only agency MBS strips was $1.5 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of March 31, 2013. The par value of our principal-only agency MBS strips was $295 million as of March 31, 2013.
[2]	Incorporates a weighted average future constant prepayment rate assumption of 9% based on forward rates as of March 31, 2013
[3]	The UPB of our interest-only securities was $1.7 billion and the weighted average contractual interest we are entitled to receive was 5.78% of this amount as of December 31, 2012. The par value of our principal-only agency MBS strips was $302 million as of December 31, 2012

Investment Securities (Components Of Investment Securities) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2013 USD ($) years	Dec. 31, 2012 USD ($) years
Weighted Average Life of Interest Only Securities \| years	6.0	5.7
Principal Balance of Securities Held as Collateral	$ 1,300	$ 1,400
Fair Value Of CMO Securities Directly Held	673	719
CMO and Interest Only, Pricincipal Only Securities, Maximum Loss Exposure	316	343
Amortized cost	75,088	83,193
Gross unrealized gains	1,405	2,099
Gross unrealized losses	(198)	(47)
Available-for-sale Securities, Fair Value Disclosure	75,779	84,699
Total agency MBS, at fair value	76,295	85,245
Total Agency Securities	76,295	85,245
Fixed-Rate [Member]
Amortized cost	73,649	81,617
Gross unrealized gains	1,355	2,043
Gross unrealized losses	(176)	25
Available-for-sale Securities, Fair Value Disclosure	74,828	83,635
Adjustable-Rate [Member]
Amortized cost	773	865
Gross unrealized gains	21	26
Gross unrealized losses	0	0
Available-for-sale Securities, Fair Value Disclosure	794	891
CMO [Member]
Amortized cost	153	170
Gross unrealized gains	4	3
Gross unrealized losses	0	0
Available-for-sale Securities, Fair Value Disclosure	157	173
Interest-Only-Strip [Member]
Amortized cost		541
Gross unrealized gains		27
Gross unrealized losses		22
Fair Value		$ 546
Interest-Only And Principal-Only Securities [Member]
Amortized cost	513
Gross unrealized gains	25
Gross unrealized losses	(22)
Fair Value	$ 516

Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2013 USD ($) years	Dec. 31, 2012 USD ($) years
Weighted Average Life of Interest Only Securities \| years	6.0	5.7
Agency securities classified as available for sale, Fair value	$ 75,779	$ 84,699
Agency securities classified as available for sale, Amortized cost	$ 74,575	$ 82,652
Weighted average coupon	3.62%	3.59%
Available For Sale Securities Weighted Average Life yield	2.73%	2.59%
Weighted Average Life Of Principal Only Securities \| years	7.0	6.4
Greater Than One Year and Less Than or Equal to Three Years [Member]
Available For Sale Securities Weighted Average Life Fair Value	$ 279	$ 1,119
Available For Sale Securities Weighted Average Life Amortized Cost	$ 272	$ 1,108
Weighted average coupon	4.54%	4.18%
Available For Sale Securities Weighted Average Life yield	3.01%	2.14%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Available For Sale Securities Weighted Average Life Fair Value	$ 17,428	$ 27,448
Available For Sale Securities Weighted Average Life Amortized Cost	$ 16,835	$ 26,750
Weighted average coupon	3.76%	3.36%
Available For Sale Securities Weighted Average Life yield	2.67%	2.29%
Greater Than Five Years [Member]
Available For Sale Securities Weighted Average Life Fair Value	$ 49,750	$ 54,054
Available For Sale Securities Weighted Average Life Amortized Cost	$ 49,132	$ 52,735
Weighted average coupon	3.68%	3.69%
Available For Sale Securities Weighted Average Life yield	2.76%	2.75%
Greater Than Ten Years [Member]
Available For Sale Securities Weighted Average Life Fair Value	$ 8,322	$ 2,078
Available For Sale Securities Weighted Average Life Amortized Cost	$ 8,336	$ 2,059
Weighted average coupon	2.96%	3.44%
Available For Sale Securities Weighted Average Life yield	2.65%	2.65%

Investment Securities (Summary Of Changes In Accumulated OCI For Available-For-Sale Security) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized gain (loss) on available-for-sale securities, net	$ (837)	$ (106)
Agency Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning OCI Balance	2,041	1,002
Unrealized gain (loss) on available-for-sale securities, net	(863)	110
Reversal of prior Period Unrealized (Gains) and Losses, Net on Realization	(26)	216
Ending OCI Balance	$ 1,204	$ 896

- Definition

Net of tax amount of unrealized holding gain (loss) before reclassification adjustments and transfers on available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e637-108580

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 115
-Paragraph 13
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 17, 22
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 130
-Paragraph 24
-Subparagraph b
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher AICPA
-Name Accounting Research Bulletin (ARB)
-Number 51
-Paragraph 38
-Subparagraph c(3)
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) - Accumulated Other Comprehensive Income (Loss) [Member] - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$ 25,963	$ 8,430
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	174	25
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	84	0
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	(2)	0
Unrealized Loss Position For - Estimated Fair Value - Total	26,047	8,430
Unrealized Loss Position For - Unrealized Loss - Total	$ (176)	$ (25)

Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Principal Balance of Securities Held as Collateral	$ 1,300		$ 1,400
Debt Instrument, Face Amount	844		908
Unrealized Gain On Derivative Instrument And Trading Securities	(1)	$ 1
Total Agency Securities	$ 76,295		85,245
Document Period End Date	Mar. 31, 2013
Proceeds from agency MBS sold	$ 0	(2,118)
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	(26)	216
Agency Securities Amortized Cost	75,088		83,193
Gain Loss on Other Debt	13	0
Agency Securities [Member]
Agency MBS sold, at cost	20,328	9,243
Proceeds from agency MBS sold	(20,302)	(9,459)
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	(26)	216
Gross gains on sale of agency MBS	87	220
Gross losses on sale of agency MBS	113	$ 4
Freddie Mac [Member]
Total Agency Securities	21,477		20,801
Available-for-sale Securities [Member]
Available For Sale Securities Par	70,956		78,486
Available-for-sale Securities [Member] \| Freddie Mac [Member]
Available For Sale Securities Par	$ 20,228		$ 19,336

Investment Securities (Summary Of Agency Securities Pledged As Collateral Under Repurchase, Other Debt, Derivative And Prime Broker Agreements) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Fair value	$ 70,094		$ 79,966
Accrued interest on pledged agency securities	202		226
Gain on sale of agency securities, net	(26)	$ 216
Restricted Cash and Cash Equivalents	499		399
Total Fair Value of Agency Securities Pledged and Accrued Interest	72,700		82,126
Repurchase Agreements [Member]
Fair value	69,537		78,400
Accrued interest on pledged agency securities	196		217
Total Fair Value of Agency Securities Pledged and Accrued Interest	69,733		78,617
Under Repurchase Agreements [Member]
Fair value	1,421		1,535
Accrued interest on pledged agency securities	4		5
Total Fair Value of Agency Securities Pledged and Accrued Interest	1,425		1,540
Under Derivative Agreements [Member]
Fair value	812		1,065
Accrued interest on pledged agency securities	2		3
Total Fair Value of Agency Securities Pledged and Accrued Interest	930		1,317
Under Prime Broker Agreements [Member] \| Fannie Mae [Member]
Fair value	229		501
Accrued interest on pledged agency securities			1
Total Fair Value of Agency Securities Pledged and Accrued Interest	612		652
Includes Sold But Not Yet Settled Securities [Member]
Fair value	71,999		81,501
Agency Securities [Member]
Cost Of Sale Of Available For Sale Securities	20,328	9,243
Gain on sale of agency securities, net	(26)	$ 216
Under Derivative Agreements [Member]
Restricted Cash and Cash Equivalents	116		249
Under Prime Broker Agreements [Member]
Restricted Cash and Cash Equivalents	$ 383		$ 150

Investment Securities (Summary Of Agency Securities Pledged As Collateral Under Repurchase Agreements By Remaining Maturity) (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Fair Value Of CMO Securities Directly Held	$ 673	$ 719
Fair value	70,958	79,935
Amortized cost	69,807	78,003
Accrued Interest on pledged agency securities	200	222
Available-for-sale Securities Pledged as Collateral	70,094	79,966
30 Days or Less [Member]
Fair value	28,076	29,284
Amortized cost	27,572	28,525
Accrued Interest on pledged agency securities	80	82
Maturity 31 To 59 Days [Member]
Fair value	14,020	21,716
Amortized cost	13,774	21,251
Accrued Interest on pledged agency securities	39	58
Maturity 60 To 90 Days [Member]
Fair value	7,321	16,188
Amortized cost	7,241	15,780
Accrued Interest on pledged agency securities	21	45
Greater than 90 Days [Member]
Fair value	21,541	12,747
Amortized cost	21,220	12,447
Accrued Interest on pledged agency securities	60	37
Repurchase Agreements [Member]
Available-for-sale Securities Pledged as Collateral	$ 69,537	$ 78,400

Repurchase Agreements And Other Debt (Narrative) (Details) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2013 USD ($) years	Dec. 31, 2012 USD ($)
Debt Instrument [Line Items]
Weighted Average Life of Other Debt \| years	5.7
Secured Debt, Dollar Rolls	$ 27,300
Risk of repurchase agreement to stockholders equity	3.00%	4.00%
Other Long-term Debt	$ 862	$ 937
Debt Instrument, Face Amount	$ 844	$ 908
Debt Instrument, Description of Variable Rate Basis, LIBOR	LIBOR
Spread Over LIBOR	42	43

Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) $ in Millions	Mar. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Debt Instrument, Face Amount	$ 844	$ 908
Borrowings Outstanding	66,260	$ 74,478
Weighted Average Days to Maturity		118
1 Month or Less
Borrowings Outstanding	$ 8,059	$ 4,011
Average Interest Rate	0.41%	0.48%
Weighted Average Days to Maturity	13	13
thirty one to ninety [Member]
Borrowings Outstanding	$ 29,461	$ 28,307
Average Interest Rate	0.42%	0.49%
Weighted Average Days to Maturity	30	37
120 to 180 days [Member]
Borrowings Outstanding	$ 11,173	$ 24,303
Average Interest Rate	0.48%	0.49%
Weighted Average Days to Maturity	68	63
210 to 270 days [Member]
Borrowings Outstanding	$ 4,436	$ 5,222
Average Interest Rate	0.49%	0.54%
Weighted Average Days to Maturity	140	79
300 to 360 days [Member]
Borrowings Outstanding	$ 8,063	$ 7,813
Average Interest Rate	0.58%	0.58%
Weighted Average Days to Maturity	216	222
390 to 720 days [Member]
Borrowings Outstanding	$ 2,099	$ 1,917
Average Interest Rate	0.63%	0.65%
Weighted Average Days to Maturity	469	564
750 to 1080 days [Member]
Borrowings Outstanding	$ 2,767	$ 2,803
Average Interest Rate	0.67%	0.69%
Weighted Average Days to Maturity	872	963
Greater than 1080 days [Member]
Borrowings Outstanding	$ 202	$ 102
Average Interest Rate	0.74%	0.73%
Weighted Average Days to Maturity	1,532	1,751
Mortgage Backed Securities, Other [Member]
Borrowings Outstanding	$ 66,260	$ 74,478
Average Interest Rate	0.47%	0.51%
Weighted Average Days to Maturity	118

Derivative and Other Hedging Instruments (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 84	$ 39
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49	52
Net Periodic Interest Rate Costs on Swaps	133	91
Fair Value of Derivative Instruments	(11)		$ 95
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	12,548		11,763
Proceeds from sales of treasury securities	12,500		11,700
Interest rate swap agreement outstanding not designated as hedge			14,450
Gain on interest only securities remeasured at fair value through earnings	(1)
Loss on interest only securities remeasured at fair value through earnings	(1)
Loss on cash flow hedge ineffectiveness		1
Gain on trading securities	1	(1)
Restricted Cash Pledged As Collateral	116
Unrealized Gain (Loss) On Derivative Instrument And Trading Securities	(98)	47
Interest Rate Contract [Member]
Fair value of interest rate swap, liability position	1,100
Agency securities, pledged as collateral against interest rate swap	812
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	(437)		$ (486)
Deferred gain loss discontinued interest rate swap expected to be reclassified from OCI to interest expense next twelve months	184
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member] \| Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49	$ 52

Derivative and Other Hedging Instruments (Remaining Interest Rate Swap Term) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Unrealized (loss) gain on derivative instruments, net	$ 49	$ 52
Notional amount of forward starting swaps	$ 26,268		$ 12,477
Remaining interest rate swap term, maximum	6 months			4 months
Not Designated as Hedging Instrument [Member]
Notional Amount	$ 51,250		$ 46,850
Average Maturity (Years)	4 years 9 months		4 years 5 months
Average Fixed Pay Rate	1.51%		1.46%
Average Receive Rate	0.28%		0.29%
Net Estimated Fair Value	$ (1,044)		$ (1,229)
Greater Than One Year and Less Than or Equal to Three Years [Member]
Notional Amount	$ 14,950		$ 14,600
Average Maturity (Years)	2 years		2 years
Average Fixed Pay Rate	1.29%		1.23%
Average Receive Rate	0.25%		0.26%
Net Estimated Fair Value	$ (309)		$ (294)
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Notional Amount	$ 19,750		$ 20,250
Average Maturity (Years)	4 years		4 years 1 month
Average Fixed Pay Rate	1.41%		1.48%
Average Receive Rate	0.27%		0.29%
Net Estimated Fair Value	$ (535)		$ (666)
Greater Than Five Years and Less than or Equal to Seven Years [Member]
Notional Amount	$ 6,100		$ 5,600
Average Maturity (Years)	6 years		6 years 1 month
Average Fixed Pay Rate	1.59%		1.53%
Average Receive Rate	0.32%		0.34%
Net Estimated Fair Value	$ (145)		$ (163)
Greater Than Seven Years and Less than or Equal to Ten Years [Member]
Notional Amount	$ 7,250		$ 5,200
Average Maturity (Years)	9 years 1 month		9 years 2 months
Average Fixed Pay Rate	1.89%		1.89%
Average Receive Rate	0.31%		0.35%
Net Estimated Fair Value	$ (37)		$ (113)
Greater Than Ten Years [Member]
Notional Amount	$ 3,200		$ 1,200
Average Maturity (Years)	10 years 4 months		10 years 2 months
Average Fixed Pay Rate	2.17%		1.79%
Average Receive Rate	0.28%		0.31%
Net Estimated Fair Value	$ (18)		$ 7
Interest Rate Swap [Member]
Average Maturity (Years)	10 years
Interest Rate Swap [Member]
Notional amount of forward starting swaps	$ 5,200		$ 1,700

Derivative and Other Hedging Instruments (Effect Of Interest Rate Swaps Designated As Hedges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivatives, Fair Value [Line Items]
Net Periodic Interest Rate Costs on Swaps	$ 133	$ 91
Loss on cash flow hedge ineffectiveness		1
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 84	$ 39

- Definition

The effective portion of gain reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References + Details

Derivative and Other Hedging Instruments (Summary Of Outstanding Forward Contracts Designated As Hedging Instruments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net Periodic Interest Rate Costs on Swaps	$ 133	$ 91
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$ 84	$ 39

- Definition

The effective portion of gain reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

+ References + Details

Derivative and Other Hedging Instruments (Effect of Forward Contracts Designated as Hedges) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Unrealized (loss) gain on derivative instruments, net	$ 49	$ 52

- Definition

+ References

+ Details

Derivative and Other Hedging Instruments (Summary of Long and Short Position of Derivative Instruments) (Details) - USD ($)
$ in Millions

Mar. 31, 2013

Dec. 31, 2012

Notional Amount

$ 26,268

$ 12,477

Derivative, Forward Settlement Value

27,294

12,775

Derivative Liability, Fair Value, Gross Liability

1,100

1,243

Derivative Asset, Fair Value, Gross Asset

27,283

12,870

Fair Value of Derivative Instruments

(11)

TBA securities Fifteen Year and Thirty Year Securities [Member]

Notional Amount

^[1]

26,218

12,327

Derivative, Forward Settlement Value

27,242

12,612

Derivative Asset, Fair Value, Gross Asset

27,231

12,708

Fair Value of Derivative Instruments

^[1]

(11)

TBA securities Fifteen Year and Thirty Year Securities [Member] | Purchase [Member]

Notional Amount

29,144

21,705

Derivative, Forward Settlement Value

30,170

22,603

Derivative Asset, Fair Value, Gross Asset

30,161

22,719

Fair Value of Derivative Instruments

(9)

116

TBA securities Fifteen Year and Thirty Year Securities [Member] | Sale [Member]

Notional Amount

(2,926)

(9,378)

Derivative, Forward Settlement Value

(2,928)

(9,991)

Derivative Liability, Fair Value, Gross Liability

(2,930)

(10,011)

Fair Value of Derivative Instruments

(2)

(20)

Forward settling securities Twenty Year Securities and ARMs [Member]

Notional Amount

^[2]

150

Derivative, Forward Settlement Value

163

Derivative Asset, Fair Value, Gross Asset

162

Fair Value of Derivative Instruments

^[2]

(1)

Forward settling securities Twenty Year Securities and ARMs [Member] | Purchase [Member]

Notional Amount

150

Derivative, Forward Settlement Value

163

Derivative Asset, Fair Value, Gross Asset

162

Fair Value of Derivative Instruments

$ 0

$ (1)

[1]	Includes 15-year and 30-year TBA securities of varying coupons
[2]	Includes 30-year fixed securities of varying coupons

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps Agreements Not Designated As Hedges) (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		$ 1
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 12,548		$ 11,763
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(110)	46
Payer Interest Rate Swaps [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	5,750	7,850
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(1,350)	0
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	51,250	38,100	46,850	$ 30,250
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	54	(44)
Payer Swaption [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	11,150	7,950
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(2,700)	(650)
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	22,900	10,500	14,450	3,200
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(44)	3
Treasury Futures [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments		1,653		783
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	77,600	22,313
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(70,261)	(24,225)
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	29,194	1,787	21,855	3,699
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(185)	67
Markit IOS Total Return Swaps - Long [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period		0
Notional Amount of Other Derivatives Not Designated as Hedging Instruments		39		41
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		1
Sale Of TBA And Forward Settling Agency Securities [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	34,333	30,829
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(40,785)	(25,579)
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	2,926	9,053	9,378	3,803
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	83	(51)
Short Sales Of U S Government Securities [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	9,935	10,990
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(9,210)	(8,005)
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	12,560	3,865	11,835	880
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(3)	52
Markit IOS Total Return Swaps - Short [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period		0
Notional Amount of Other Derivatives Not Designated as Hedging Instruments		194		$ 206
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		$ (3)
Derivative liabilities, at fair value [Member]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(1,217)		(1,264)
Derivative liabilities, at fair value [Member] \| Payer Interest Rate Swaps [Member]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(1,100)		(1,243)
Derivative liabilities, at fair value [Member] \| Treasury Futures [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	(14)		0
Derivative liabilities, at fair value [Member] \| Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	(95)		(1)
Derivative liabilities, at fair value [Member] \| Sale Of TBA And Forward Settling Agency Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(8)		(20)
Derivative assets, at fair value [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	480		301
Derivative assets, at fair value [Member] \| Payer Interest Rate Swaps [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value			14
Derivative assets, at fair value [Member] \| Payer Swaption [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value			171
Derivative assets, at fair value [Member] \| Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	86		116
Derivative assets, at fair value [Member] \| Sale Of TBA And Forward Settling Agency Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	6		0
Greater Than One Year and Less Than or Equal to Three Years [Member]
Notional Amount of Interest Rate Derivatives	14,950		14,600
Notional Amount	$ 14,950		$ 14,600
Average Fixed Pay Rate	1.29%		1.23%
Average Receive Rate	0.25%		0.26%
Net Estimated Fair Value	$ (309)		$ (294)
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.25%		0.26%
Derivative, Average Remaining Maturity	2 years		2 years
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Notional Amount of Interest Rate Derivatives	$ 19,750		$ 20,250
Notional Amount	$ 19,750		$ 20,250
Average Fixed Pay Rate	1.41%		1.48%
Average Receive Rate	0.27%		0.29%
Net Estimated Fair Value	$ (535)		$ (666)
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.27%		0.29%
Derivative, Average Remaining Maturity	4 years		4 years 1 month
Greater Than Five Years and Less than or Equal to Seven Years [Member]
Notional Amount of Interest Rate Derivatives	$ 6,100		$ 5,600
Notional Amount	$ 6,100		$ 5,600
Average Fixed Pay Rate	1.59%		1.53%
Average Receive Rate	0.32%		0.34%
Net Estimated Fair Value	$ (145)		$ (163)
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.32%		0.34%
Derivative, Average Remaining Maturity	6 years		6 years 1 month
Greater Than Seven Years and Less than or Equal to Ten Years [Member]
Notional Amount of Interest Rate Derivatives	$ 7,250		$ 5,200
Notional Amount	$ 7,250		$ 5,200
Average Fixed Pay Rate	1.89%		1.89%
Average Receive Rate	0.31%		0.35%
Net Estimated Fair Value	$ (37)		$ (113)
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.31%		0.35%
Derivative, Average Remaining Maturity	9 years 1 month		9 years 2 months
Greater Than Ten Years [Member]
Notional Amount of Interest Rate Derivatives	$ 3,200		$ 1,200
Notional Amount	$ 3,200		$ 1,200
Average Fixed Pay Rate	2.17%		1.79%
Average Receive Rate	0.28%		0.31%
Net Estimated Fair Value	$ (18)		$ 7
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.28%		0.31%
Derivative, Average Remaining Maturity	10 years 4 months		10 years 2 months
Not Designated as Hedging Instrument [Member]
Notional Amount of Interest Rate Derivatives	$ 51,250		$ 46,850
Notional Amount	$ 51,250		$ 46,850
Average Fixed Pay Rate	1.51%		1.46%
Average Receive Rate	0.28%		0.29%
Net Estimated Fair Value	$ (1,044)		$ (1,229)
Interest Rate Derivative Not Designated As Hedging Instruments Average receive Rate	0.28%		0.29%
Derivative, Average Remaining Maturity	4 years 9 months		4 years 5 months

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps Agreements Designated As Hedges in the Future) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)
Fair Value			$ 171
Average Months to Expiration		21
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments			$ 14,450
Pay Rate		2.99%
Receive Rate		1M / 3M LIBOR
Term (Years)			7 years 9 months 12 days
Payer Swaption [Member]
Cost	$ 438
Fair Value	$ 332
Average Months to Expiration	17
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 22,900
Pay Rate	2.81%
Receive Rate	1M / 3M LIBOR
Term (Years)	7 years 11 months
Less Than or Equal to One Year [Member] \| Payer Swaption [Member]
Cost	$ 169	$ 76
Fair Value	$ 91		$ 15
Average Months to Expiration	7	4
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 12,100		$ 5,150
Pay Rate	2.49%	2.65%
Receive Rate	1M / 3M LIBOR	1M / 3M LIBOR
Term (Years)	8 years 5 months		8 years 6 months 24 days
Greater Than One Year and Less Than or Equal to Three Years [Member]
Cost		$ 274
Greater Than One Year and Less Than or Equal to Three Years [Member] \| Payer Swaption [Member]
Cost	$ 81	$ 65
Fair Value	$ 52		$ 34
Average Months to Expiration	17	19
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 4,200		$ 4,050
Pay Rate	2.81%	2.82%
Receive Rate	3M LIBOR	3M LIBOR
Term (Years)	6 years 9 months		6 years 8 months
greater than two years less than or equal to three years [Member] \| Payer Swaption [Member]
Cost	$ 139	$ 97
Fair Value	$ 137		$ 87
Average Months to Expiration	32	33
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 5,000		$ 3,900
Pay Rate	3.42%	3.51%
Receive Rate	3M LIBOR	3M LIBOR
Term (Years)	8 years 6 months		8 years 6 months 24 days
greater than three years less than or equal to four years [Member] \| Payer Swaption [Member]
Cost	$ 12	$ 12
Fair Value	$ 13		$ 11
Average Months to Expiration	43	46
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 450		$ 450
Pay Rate	3.20%	3.20%
Receive Rate	3M LIBOR	3M LIBOR
Term (Years)	6 years 1 month		6 years 1 month 12 days
greater than four years less than or equal to five years [Member] \| Payer Swaption [Member]
Cost	$ 37	$ 24
Fair Value	$ 39		$ 24
Average Months to Expiration	57	59
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 1,150		$ 900
Pay Rate	3.51%	3.33%
Receive Rate	3M LIBOR	3M LIBOR
Term (Years)	4 years 6 months		5 years

Derivative and Other Hedging Instruments (Summary of Outstanding Total Return Swaps) (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Notional Amount	$ 26,268	$ 12,477
Fair Value of Derivative Instruments	$ (11)	$ 95

Derivative and Other Hedging Instruments (Summary Of Derivatives Outstanding Not Designated As Hedging Instruments) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)
Interest Rate Derivatives, at Fair Value, Net			$ 171
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration		21
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments			14,450
Gain Loss on Other Debt	$ 13	$ 0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(110)	46
Notional Amount	26,268		$ 12,477
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49	52
Gain (Loss) on Cash Flow Hedge Ineffectiveness, Net		$ 1
Derivative, Higher Remaining Maturity Range	6 months			4 months
Loss on interest only securities remeasured at fair value through earnings	$ (1)
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate		2.99%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate		1M / 3M LIBOR
Derivatives Average Term			7 years 9 months 12 days
Derivative assets, at fair value [Member]
Derivative assets not designated as hedging instruments	480		$ 301
Derivative liabilities, at fair value [Member]
Derivative liabilities not designated as hedging instruments	(1,217)		(1,264)
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	29,194	$ 1,787	21,855	$ 3,699
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(185)	67
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(70,261)	(24,225)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	77,600	22,313
Purchases Of TBAs And Forward Settling Agency Securities [Member] \| Derivative assets, at fair value [Member]
Derivative assets not designated as hedging instruments	86		116
Purchases Of TBAs And Forward Settling Agency Securities [Member] \| Derivative liabilities, at fair value [Member]
Derivative assets not designated as hedging instruments	(95)		(1)
Sale Of TBA And Forward Settling Agency Securities [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	2,926	9,053	9,378	3,803
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	83	(51)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(40,785)	(25,579)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	34,333	30,829
Sale Of TBA And Forward Settling Agency Securities [Member] \| Derivative assets, at fair value [Member]
Derivative assets not designated as hedging instruments	6		0
Sale Of TBA And Forward Settling Agency Securities [Member] \| Derivative liabilities, at fair value [Member]
Derivative liabilities not designated as hedging instruments	(8)		(20)
Interest Rate Swaps [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	51,250	38,100	46,850	30,250
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	54	(44)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(1,350)	0
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	5,750	7,850
Interest Rate Swaps [Member] \| Derivative assets, at fair value [Member]
Derivative assets not designated as hedging instruments			14
Interest Rate Swaps [Member] \| Derivative liabilities, at fair value [Member]
Derivative liabilities not designated as hedging instruments	(1,100)		(1,243)
Markit IOS Total Return Swaps - Short [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments		194		206
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		(3)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period		0
Payer Swaption [Member]
Options At Cost	438
Interest Rate Derivatives, at Fair Value, Net	$ 332
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	17
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 22,900
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	22,900	10,500	14,450	3,200
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(44)	3
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(2,700)	(650)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	$ 11,150	7,950
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	2.81%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	1M / 3M LIBOR
Derivatives Average Term	7 years 11 months
Payer Swaption [Member] \| Derivative assets, at fair value [Member]
Derivative assets not designated as hedging instruments			171
Short Sales Of U S Government Securities [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments	$ 12,560	3,865	$ 11,835	880
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(3)	52
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(9,210)	(8,005)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	$ 9,935	10,990
Markit IOS Total Return Swaps - Long [Member]
Notional Amount of Other Derivatives Not Designated as Hedging Instruments		39		$ 41
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net		1
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period		0
Not Designated as Hedging Instrument [Member]
Derivative, Average Remaining Maturity	4 years 9 months		4 years 5 months
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	437		$ 486
Deferred gain loss discontinued interest rate swap expected to be reclassified from OCI to interest expense next twelve months	$ 184
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member] \| Interest Rate Swaps [Member]
Derivative, Average Remaining Maturity	2 years 8 months 10 days
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member] \| Interest Rate Swap [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49	52
Treasury Futures [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(783)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period		1,653
Markit IOS Total Return Swaps - Short [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(12)
Markit IOS Total Return Swaps - Long [Member]
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(2)
Interest Rate Swap [Member]
Notional Amount	5,200		1,700
Less Than or Equal to One Year [Member] \| Payer Swaption [Member]
Options At Cost	169	$ 76
Interest Rate Derivatives, at Fair Value, Net	$ 91		15
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	7	4
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 12,100		$ 5,150
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	2.49%	2.65%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	1M / 3M LIBOR	1M / 3M LIBOR
Derivatives Average Term	8 years 5 months		8 years 6 months 24 days
Greater Than One Year and Less Than or Equal to Three Years [Member]
Options At Cost		$ 274
Derivative, Average Remaining Maturity	2 years		2 years
Greater Than One Year and Less Than or Equal to Three Years [Member] \| Payer Swaption [Member]
Options At Cost	$ 81	$ 65
Interest Rate Derivatives, at Fair Value, Net	$ 52		$ 34
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	17	19
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 4,200		$ 4,050
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	2.81%	2.82%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M LIBOR	3M LIBOR
Derivatives Average Term	6 years 9 months		6 years 8 months
greater than two years less than or equal to three years [Member] \| Payer Swaption [Member]
Options At Cost	$ 139	$ 97
Interest Rate Derivatives, at Fair Value, Net	$ 137		$ 87
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	32	33
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 5,000		$ 3,900
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	3.42%	3.51%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M LIBOR	3M LIBOR
Derivatives Average Term	8 years 6 months		8 years 6 months 24 days
greater than three years less than or equal to four years [Member] \| Payer Swaption [Member]
Options At Cost	$ 12	$ 12
Interest Rate Derivatives, at Fair Value, Net	$ 13		$ 11
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	43	46
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 450		$ 450
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	3.20%	3.20%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M LIBOR	3M LIBOR
Derivatives Average Term	6 years 1 month		6 years 1 month 12 days
greater than four years less than or equal to five years [Member] \| Payer Swaption [Member]
Options At Cost	$ 37	$ 24
Interest Rate Derivatives, at Fair Value, Net	$ 39		$ 24
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	57	59
Notional Amount of Interest Rate Derivative Instruments Not Designated as Hedging Instruments	$ 1,150		$ 900
Interest Rate Derivative Not Designated As Hedging instruments Pay Rate	3.51%	3.33%
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M LIBOR	3M LIBOR
Derivatives Average Term	4 years 6 months		5 years

Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Unrealized Gain On Derivative Instrument And Trading Securities	$ (1)	$ 1
Amount Gain/(Loss) Recognized in Income on Derivatives	(110)	46
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Notional Amount	21,855	3,699
Additions	77,600	22,313
Settlement, Expirations or Exercise	(70,261)	(24,225)
Notional Amount	29,194	1,787
Amount Gain/(Loss) Recognized in Income on Derivatives	(185)	67
Sale Of TBA And Forward Settling Agency Securities [Member]
Notional Amount	9,378	3,803
Additions	34,333	30,829
Settlement, Expirations or Exercise	(40,785)	(25,579)
Notional Amount	2,926	9,053
Amount Gain/(Loss) Recognized in Income on Derivatives	83	(51)
Payer Interest Rate Swaps [Member]
Notional Amount	46,850	30,250
Additions	5,750	7,850
Settlement, Expirations or Exercise	(1,350)	0
Notional Amount	51,250	38,100
Amount Gain/(Loss) Recognized in Income on Derivatives	54	(44)
Payer Swaption [Member]
Notional Amount	14,450	3,200
Additions	11,150	7,950
Settlement, Expirations or Exercise	(2,700)	(650)
Notional Amount	22,900	10,500
Amount Gain/(Loss) Recognized in Income on Derivatives	(44)	3
Short Sales Of U S Government Securities [Member]
Notional Amount	11,835	880
Additions	9,935	10,990
Settlement, Expirations or Exercise	(9,210)	(8,005)
Notional Amount	12,560	3,865
Amount Gain/(Loss) Recognized in Income on Derivatives	(3)	52
Treasury Futures [Member]
Notional Amount		783
Notional Amount		1,653
Treasury Futures Short [Member]
Notional Amount	0
Additions	800
Settlement, Expirations or Exercise	0
Notional Amount	800
Amount Gain/(Loss) Recognized in Income on Derivatives	$ (15)	21
Markit IOS Total Return Swaps - Long [Member]
Notional Amount		41
Additions		0
Notional Amount		39
Amount Gain/(Loss) Recognized in Income on Derivatives		1
Markit IOS Total Return Swaps - Short [Member]
Notional Amount		206
Additions		0
Notional Amount		194
Amount Gain/(Loss) Recognized in Income on Derivatives		$ (3)

Fair Value Measurements (Details) - USD ($) $ in Millions	3 Months Ended
Fair Value Measurements (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	$ 74,874	$ 83,710
Derivative Assets	480	301
Other Long-term Debt	862	937
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	(12,548)	(11,763)
Derivative Liabilities	$ (1,217)	(1,264)
Transfers between hierarchy levels	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Debt Instrument, Fair Value Disclosure		937
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure		0
Liabilities, Fair Value Disclosure	$ 12,548	11,763
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	76,775	85,546
Liabilities, Fair Value Disclosure	2,079	2,201
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	(117)	(21)
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Swaptions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		171
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets		14
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Other derivative instruments [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Assets	92	116
Derivative assets, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	480	301
Derivative liabilities, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(1,217)	(1,264)
Interest Rate Swaps [Member] \| Derivative assets, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		14
Interest Rate Swaps [Member] \| Derivative assets, at fair value [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	56
Interest Rate Swaps [Member] \| Derivative liabilities, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	(1,100)	(1,243)
Payer Swaption [Member] \| Derivative assets, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value		171
Payer Swaption [Member] \| Derivative assets, at fair value [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Swaptions [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	332
Treasury Futures [Member] \| Derivative liabilities, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	(14)	0
Collateralized Mortgage Backed Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, Mortgages, Mortgage-backed and Asset-backed Securities, at Fair Value	76,295	85,245
Interest Rate Swap [Member] \| Interest Rate Swaps [Member] \| Derivative liabilities, at fair value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liabilities	$ (1,100)
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value		$ 1,243

Stockholders' Equity (Summary of Follow-on Public Offerings of Common Stock) (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 423,000
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	(837,000)	$ (106,000)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49,000	52,000
Total Reclass of Other Comprehensive Income	75,000
Other comprehensive income (loss)	$ (788,000)	(54,000)
Public offering price per share	$ 31.34
Public offering of common stock	57.5
Proceeds from Issuance of Common Stock	$ 1,802,000	$ 2,205,000
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ 767,000		$ 1,555,000
At the Market Offering Program [Member]
Common Stock, Capital Shares Reserved for Future Issuance	16.7
Common Stock [Member]
Public offering of common stock	57.6	75.8
Dividend Reinvestment And Direct Stock Purchase Plan [Member]
Common Stock, Capital Shares Reserved for Future Issuance	4.7
Agency Securities [Member]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	$ 1,204,000	$ 896,000	2,041,000	$ 1,002,000
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	(863,000)	110,000
Other Comprehensive Income Reclassification Adjustment For Sale Of Security Reversal Of Prior Period Unrealized Gain And Losses On Realization	26,000	(216,000)
net current period other comprehensive income	(837,000)
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49,000
net current period other comprehensive income	49,000
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	(437,000)		$ (486,000)
Interest Rate Swap [Member] \| Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49,000	$ 52,000

Stockholders' Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Spread Over LIBOR	42		43
Preferred stock, shares issued	6.9		6.9
Issuance of common stock, value	$ 1,802	$ 2,205
Public offering of common stock	57.5
Preferred Stock, Par or Stated Value Per Share	$ 0.01		$ 0.01
Stock Repurchase Program, Authorized Amount	$ 500
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49	52
Total Reclass of Other Comprehensive Income	$ 75
At the Market Offering Program [Member]
Shares available for issuance	16.7
Dividend Reinvestment And Direct Stock Purchase Plan [Member]
Shares available for issuance	4.7
Agency Securities [Member]
Other Comprehensive Income Reclassification Adjustment For Sale Of Security Reversal Of Prior Period Unrealized Gain And Losses On Realization	$ 26	(216)
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49
Interest Rate Swap [Member] \| Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49	$ 52

Subsequent Event (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Subsequent Event [Line Items]
Stock Repurchase Program, Authorized Amount	$ 500
Issuance of common stock, shares	57.5
Preferred stock, shares issued	6.9		6.9
Dividends declared per common share	$ 1.25	$ 1.25
Preferred Stock, Par or Stated Value Per Share	0.01		$ 0.01
Sale of Stock, Price Per Share	$ 31.34

Quarterly Results (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Interest income:
Interest Income, Securities, Mortgage Backed	$ 547	$ 514
Interest Expense	140	106
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	(26)	216
Unrealized Gain (Loss) On Derivative Instrument And Trading Securities	(98)	47
Management fees	33	22
General and Administrative Expense	9	6
Excise and REIT Income tax	10	2
Net income (loss)	231	641
Other comprehensive income:
Unrealized gain (loss) on available-for-sale securities, net	(837)	(106)
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49	52
Preferred Stock Dividends, Income Statement Impact	3	0
Comprehensive income available to common shareholders	(560)	587
Net income (loss) available (attributable) to common shareholders	$ 228	$ 641
Weighted Average Number Of Common Shares Outstanding Basic And Diluted	356.2	240.6
Common Stock, Dividends, Per Share, Declared	$ 1.25	$ 1.25
Net interest income	$ 407	$ 408
Other income (loss):
Total other income (loss), net	(124)	263
Expenses:
Total expenses	42	28
Income (loss) before income tax (benefit)	241	643
Other comprehensive income	(788)	(54)
Comprehensive income	$ (557)	$ 587
Net income per common share - basic and diluted	$ 0.64	$ 2.66
Comprehensive income per share - basic and diluted	$ (1.57)	$ 2.44
Accumulated Other Comprehensive Income (Loss) [Member]
Other comprehensive income:
Unrealized gain (loss) on available-for-sale securities, net	$ (837)	$ (106)
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other comprehensive income:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	49
Interest Rate Swap [Member] \| Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Other comprehensive income:
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$ 49	$ 52

Income Taxes (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Dividends Payable [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 1.25	$ 1.25
Dividends, Common Stock, Cash	$ (496)	$ (286)

Management Agreement and Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Related Party Transaction [Line Items]
Management fees	$ 33	$ 22
Proceeds from Issuance of Common Stock	$ 1,802	$ 2,205

Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2013	Dec. 31, 2012
Offsetting Assets and Liabilities [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ 1,100	$ 1,243
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	1,100	1,243
Available-for-sale Securities Pledged as Collateral	70,094	79,966
Restricted Cash Pledged As Collateral	116
Amount of Liabilities and Collateral Pledged, Net	7
Derivative Asset, Fair Value, Gross Asset	27,283	12,870
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	388	185
Obligation to Return Securities Received as Collateral	(11,361)	(10,667)
Receivable Under Reverse Repurchase Agreements	12,291	11,818
Receivable under Reverse Repurchase Agreement not offset against collateral	12,291	11,818
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	12,548	11,763
obligation to return cash collateral received	(1,231)	(1,157)
Amount of Net Assets and Collateral Received, Net	87	179
Total Derivative, Other Hedging Instruments and Other Assets, Gross	12,679	12,003
Total Derivative Other Hedging Instruments and Other Assets Not Offset vs Collateral	12,679	12,003
Borrowings Outstanding	66,260	74,478
Total Derivative, Other Hedging Instruments and Other Liabilities, Gross	67,360	75,721
Interest Rate Swap and Swaption [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	(388)	(185)
Restricted Cash Pledged As Collateral	(705)	(1,058)
Obligation to Return Securities Received as Collateral	(388)	(185)
Interest Rate Swap and Swaption [Member]
Offsetting Assets and Liabilities [Line Items]
Derivative Asset, Fair Value, Gross Asset	388	185
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	(10,973)	(10,482)
Restricted Cash Pledged As Collateral	(55,287)	(63,996)
Repurchase Agreements [Member] \| Interest Rate Swap and Swaption [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	(11,361)	(10,667)
Restricted Cash Pledged As Collateral	(55,992)	(65,054)
Reverse Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ (10,973)	$ (10,482)