AGNC Investment (AGNC) 10-Q 9 May 14 2014 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2014	Apr. 30, 2014
Document and Entity Information [Abstract]	'	'
Document Type	'10-Q	'
Amendment Flag	'false	'
Document Period End Date	31-Mar-14	'
Document Fiscal Year Focus	'2014	'
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	'	352,788,707
Trading Symbol	'AGNC	'
Entity Well-known Seasoned Issuer	'Yes	'
Entity Voluntary Filers	'No	'
Entity Current Reporting Status	'Yes	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Assets:	'	'
Agency securities, at fair value	$54,960	$64,482
Agency securities transferred to consolidated variable interest entities, at fair value	1,417	1,459
U.S. Treasury securities, at fair value	196	3,822
REIT equity securities, at fair value	352	237
Cash and cash equivalents	1,726	2,143
Restricted cash	269	101
Derivative assets, at fair value	686	1,194
Receivable for agency securities sold	799	652
Receivable under reverse repurchase agreements	6,685	1,881
Other assets	228	284
Total assets	67,318	76,255
Liabilities:	'	'
Repurchase agreements	49,729	63,533
Other debt	874	910
Payable for agency securities purchased	324	118
Derivative liabilities, at fair value	417	422
Dividend payable	232	235
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	6,658	1,848
Accounts payable and other accrued liabilities	270	492
Total liabilities	58,504	67,558
Stockholders' equity:	'	'
Preferred Stock, Value, Issued	167	167
Common stock	4	4
Additional paid-in capital	10,332	10,406
Retained earnings (deficit)	-870	-497
Accumulated other comprehensive income	-819	-1,383
Total stockholders' equity	8,814	8,697
Total liabilities and stockholders' equity	$67,318	$76,255

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, except Per Share data, unless otherwise specified
Available-for-sale Securities Pledged as Collateral	$51,850	$62,205
Trading Securities Pledged as Collateral	196	3,778
Assets Pledged included in Receivable for Securities Sold	772	622
Preferred Stock, Par or Stated Value Per Share	$0.01	$0.01
Preferred Stock, Shares Authorized	10	10
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	600
Common Stock, Shares, Issued	352.8	356.2
Common Stock, Shares, Outstanding	352.8	356.2

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Interest income:	'	'
Interest income	$399	$547
Interest expense	108	140
Net interest income	291	407
Other income, net:	'	'
Gain on sale of agency securities, net	-19	-26
(Loss) gain on derivative instruments and other securities, net	-378	-98
Total other income, net	-397	-124
Expenses:	'	'
Management fees	29	33
General and administrative expenses	6	9
Total expenses	35	42
Income before income tax	-141	241
Income tax benefit, net	0	10
Dividend on preferred stock	3	3
Net income	-141	231
Net (loss) income (attributable) available to common shareholders	-144	228
Other comprehensive income (loss):	'	'
Unrealized gain (loss) on available-for-sale securities, net	521	-837
Unrealized (loss) gain on derivative instruments, net	43	49
Other comprehensive income (loss)	564	-788
Comprehensive income	423	-557
Dividend on preferred stock	3	3
Comprehensive income available to common shareholders	$420	($560)
Weighted average number of common shares outstanding-basic and diluted	354.8	356.2
Net income per common share - basic and diluted	($0.41)	$0.64
Comprehensive income per share - basic and diluted	$1.18	($1.57)
Dividends declared per common share	$0.65	$1.25

Consolidated_Statement_of_Stoc

Consolidated Statement of Stockholders' Equity (USD $)	Total	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
In Millions, unless otherwise specified
Balance, value at Dec. 31, 2012	$10,896	$167	$3	$9,460	($289)	$1,555
Balance, Common Stock, shares at Dec. 31, 2012	'	'	338.9	'	'	'
Balance, Preferred Stock, shares at Dec. 31, 2012	'	6.9	'	'	'	'
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	'	'	'	'	49
Issuance of common stock, value	1,802	'	1	1,801	'	'
Dividends, Preferred Stock, Cash	-3	'	'	'	-3	'
Issuance of common stock, shares	'	'	57.6	'	'	'
Common dividends declared	496	'	'	'	496	'
Balance, value at Mar. 31, 2013	11,642	167	4	11,261	-557	767
Balance, Common Stock, shares at Mar. 31, 2013	'	'	396.5	'	'	'
Balance, Preferred Stock, shares at Mar. 31, 2013	'	6.9	'	'	'	'
Balance, value at Dec. 31, 2013	8,697	167	4	10,406	-497	-1,383
Balance, Common Stock, shares at Dec. 31, 2013	356.2	'	356.2	'	'	'
Balance, Preferred Stock, shares at Dec. 31, 2013	6.9	6.9	'	'	'	'
Net income	-141	'	'	'	'	'
Other comprehensive income (loss):	'	'	'	'	'	'
Unrealized gain (loss) on available-for-sale securities, net	521	'	'	'	'	521
Unrealized (loss) gain on derivative instruments, net	43	'	'	'	'	43
Stock Repurchased During Period, Shares	-3.4	'	-3.4	'	'	'
Dividends, Preferred Stock, Cash	-3	'	'	'	-3	'
Stock Repurchased During Period, Value	-74	'	-74	'	'	'
Common dividends declared	229	'	'	'	229	'
Balance, value at Mar. 31, 2014	$8,814	$167	$4	$10,332	($870)	($819)
Balance, Common Stock, shares at Mar. 31, 2014	352.8	'	352.8	'	'	'
Balance, Preferred Stock, shares at Mar. 31, 2014	6.9	6.9	'	'	'	'

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Operating activities:	'	'
Net income (loss)	($141)	$231
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Amortization of agency securities premiums and discounts, net	142	134
Amortization of accumulated other comprehensive loss on interest rate swaps de-designated as qualifying hedges	43	49
Gain on sale of agency securities, net	19	26
Loss (gain) on derivative instruments and other securities, net	378	98
Increase in other assets	60	19
Increase in accounts payable and other accrued liabilities	-13	-39
Net cash provided by operating activities	488	518
Investing activities:	'	'
Purchases of agency securities	-1,403	-15,294
Proceeds from sale of agency securities	9,545	19,568
Principal collections on agency securities	1,853	2,634
Purchases of U.S. Treasury securities	-4,343	-9,222
Proceeds from sale of U.S. Treasury securities	12,807	10,001
Proceeds from reverse repurchase agreements	-4,804	-473
Net (payments) receipts on other derivative instruments not designated as qualifying hedges	58	-329
Purchases of REIT equity securities	-204	0
Proceeds from sale of REIT equity securities	86	0
Decrease in restricted cash	-168	-100
Other investing cash flows, net	-183	0
Net cash used in investing activities	13,244	6,785
Financing activities:	'	'
Proceeds from repurchase arrangements, net	79,314	96,511
Payments made on repurchase agreements	-93,118	-104,729
Repayments on other debt	-36	-64
Net proceeds from common stock issuances	0	1,802
Payments made on common stock repurchases	-74	0
Stock Repurchased During Period, Value	-74	'
Cash dividends paid	-235	-427
Net cash provided by financing activities	-14,149	-6,907
Net change in cash and cash equivalents	-417	396
Cash and cash equivalents at beginning of period	2,143	2,430
Cash and cash equivalents at end of period	$1,726	$2,826

Unaudited_Interim_Consolidated

Unaudited Interim Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2014
Quarterly Financial Information Disclosure [Abstract]	'
Quarterly Financial Information [Text Block]	'
	Unaudited Interim Consolidated Financial Statements
	The unaudited 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 interim 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.

Organization

Organization	3 Months Ended
	Mar. 31, 2014
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 are externally managed by American Capital AGNC Management, LLC (our "Manager"), an affiliate of American Capital, Ltd. ("American Capital").
	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"). 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 net 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 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 a government-sponsored enterprise, 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") and in other assets reasonably related to agency securities.
	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.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2014
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 sell any of our agency securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our agency 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 (loss) ("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 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 and principal-only securities are included in agency securities, at fair value on the accompanying consolidated balance sheets.
	REIT equity securities represent investments in the common stock of other publicly traded mortgage REITs that invest predominantly in agency MBS. We designate our investments in REIT equity securities as trading securities and report them at fair value on the accompanying consolidated balance sheets.
	We estimate the fair value of our agency 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, benchmark 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. We estimate the fair value of our REIT equity securities on a market approach using "Level 1" inputs based on quoted market prices. Refer to Note 8 for further discussion of fair value measurements.
	We evaluate our agency securities for other-than-temporary impairment ("OTTI") on at least a quarterly basis. The determination of whether a security is other-than-temporarily impaired may involve judgments and assumptions based on subjective and objective factors. When a security is impaired, an OTTI is considered to have occurred if any one of the following three conditions exist as of the financial reporting date: (i) we intend to sell the security (that is, a decision has been made to sell the security), (ii) it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis or (iii) we do not expect to recover the security's amortized cost basis, even if we do not intend to sell the security and it is not more likely than not that we will be required to sell the security. A general allowance for unidentified impairments in a portfolio of securities is not permitted.
	If either of the first two conditions exists as of the financial reporting date, 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. If the third condition exists, the OTTI is separated into (i) the amount relating to credit loss (the "credit component") and (ii) the amount relating to all other factors (the "non-credit components"). Only the credit component is recognized in earnings, with the non-credit components recognized in OCI. However, in evaluating if the third condition exists, our investments in agency securities typically would not have a credit component since the principal and interest are guaranteed by a GSE and, therefore, any unrealized loss is not the result of a credit loss. In addition, since we designate our agency securities as available-for-sale securities with unrealized gains and losses recognized in OCI, any impairment loss for non-credit components is already recognized in OCI.
	The liquidity of the agency securities market allows us to obtain competitive bids and execute on a sale transaction typically within a day of making the decision to sell a security and, therefore, we generally do not make decisions to sell specific agency securities until shortly prior to initiating a sell order. In some instances, we may sell specific agency securities by delivering such securities into existing short to-be-announced ("TBA") contracts. TBA market conventions require the identification of the specific securities to be delivered no later than 48 hours prior to settlement. If we settle a short TBA contract through the delivery of securities, we will generally identify the specific securities to be delivered within one to two days of the 48-hour deadline.
	Interest Income
	Interest income is accrued based on the outstanding principal amount of the investment securities and their contractual terms. Premiums or discounts associated with the purchase of investment securities are amortized or accreted into interest income, respectively, 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 its 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) the actual prepayments to date plus our currently 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.
	Derivative Instruments
	We use a variety of derivative instruments to 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 ("swaptions"). We also utilize forward contracts for the purchase or sale of agency MBS securities on a generic pool basis, or a TBA contract, 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 and principal-only securities.
	We may also enter into TBA contracts as a means of investing in and financing agency securities (thereby increasing our "at risk" leverage) or as a means of disposing of or reducing our exposure to agency securities (thereby reducing our "at risk" leverage). Pursuant to TBA contracts, we agree to purchase or sell, 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 or long position (referred to as a "pair off"), net settling the paired off positions for cash, and simultaneously purchasing or selling a similar TBA contract for a later settlement date. This transaction is commonly referred to as a "dollar roll." The agency securities purchased or sold 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/loss." 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 the 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 September 30, 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 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 swaps") with terms up to 20 years. The floating rate we receive under our swap agreements has the effect of offsetting the repricing characteristics of our repurchase agreements and cash flows on such liabilities. Our swap agreements are privately negotiated in the over−the−counter ("OTC") market and may be centrally cleared through a registered commodities exchange ("centrally cleared swaps").
	We estimate the fair value of our centrally cleared interest rate swaps using the daily settlement price determined by the respective exchange. Centrally cleared swaps are valued by the exchange using a pricing model that references the underlying rates including the overnight index swap rate and LIBOR forward rate to produce the daily settlement price.
	We estimate the fair value of our "non-centrally cleared" 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 the 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 statements 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.
	Our interest rate swaption agreements are privately negotiated in the OTC market and are not subject to central clearing. 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 may 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 or disposing of 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 either the TBA contracts do not settle in the shortest period of time possible or 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.
	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 and U.S. Treasury futures contracts are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.

Investment_Securities

Investment Securities	3 Months Ended
	Mar. 31, 2014
Available-for-sale Securities [Abstract]	'
Investment Securities	'
	Investment Securities
	As of March 31, 2014, we had agency MBS of $56.4 billion at fair value, with a total cost basis of $56.9 billion. The net unamortized premium balance on our agency MBS as of March 31, 2014 was $2.6 billion, including interest and principal-only strips. The following tables summarize our investments in agency MBS as of March 31, 2014 (dollars in millions):
			31-Mar-14
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	42,131		$	11,730			$	209			$	54,070
	Unamortized discount		(17		)	(6		)		—				(23		)
	Unamortized premium		1,887			573				6				2,466
	Amortized cost		44,001			12,297				215				56,513
	Gross unrealized gains		238			93				4				335
	Gross unrealized losses		(646		)	(257		)		—				(903		)
	Total available-for-sale agency MBS, at fair value		43,593			12,133				219				55,945
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		386			29				—				415
	Gross unrealized gains		20			4				—				24
	Gross unrealized losses		(6		)	(1		)		—				(7		)
	Total agency MBS remeasured at fair value through earnings		400			32				—				432
	Total agency MBS, at fair value		$	43,993		$	12,165			$	219			$	56,377
	Weighted average coupon as of March 31, 2014 2		3.62		%	3.75		%		3.54		%		3.65		%
	Weighted average yield as of March 31, 2014 3		2.7		%	2.82		%		1.66		%		2.72		%
	Weighted average yield for the quarter ended March 31, 2014 3		2.53		%	2.61		%		1.67		%		2.54		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.3 billion and the weighted average contractual interest we are entitled to receive was 5.49% of this amount as of March 31, 2014. The par value of our principal-only agency MBS strips was $265 million as of March 31, 2014.
	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, 2014.
	3	Incorporates a weighted average future constant prepayment rate assumption of 8% based on forward rates as of March 31, 2014.
			31-Mar-14
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	54,056		$	307			$	(902	)		$	53,461
	Adjustable rate		1,176			19				—				1,195
	CMO		1,281			9				(1		)		1,289
	Interest-only and principal-only strips		415			24				(7		)		432
	Total agency MBS		$	56,928		$	359			$	(910	)		$	56,377
	As of December 31, 2013, we had agency MBS of $65.9 billion at fair value, with a total cost basis of $67.0 billion. The net unamortized premium balance on our agency MBS as of December 31, 2013 was $3.0 billion, including interest and principal-only strips. The following tables summarize our investments in agency MBS as of December 31, 2013 (dollars in millions):
			December 31, 2013
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	50,914		$	12,640			$	223			$	63,777
	Unamortized discount		(25		)	(7		)		—				(32		)
	Unamortized premium		2,210			631				7				2,848
	Amortized cost		53,099			13,264				230				66,593
	Gross unrealized gains		181			74				5				260
	Gross unrealized losses		(991		)	(358		)		—				(1,349		)
	Total available-for-sale agency MBS, at fair value		52,289			12,980				235				65,504
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		400			32				—				432
	Gross unrealized gains		13			3				—				16
	Gross unrealized losses		(9		)	(2		)		—				(11		)
	Total agency MBS remeasured at fair value through earnings		404			33				—				437
	Total agency MBS, at fair value		$	52,693		$	13,013			$	235			$	65,941
	Weighted average coupon as of December 31, 2013 2		3.53		%	3.78		%		3.56		%		3.58		%
	Weighted average yield as of December 31, 2013 3		2.66		%	2.87		%		1.66		%		2.7		%
	Weighted average yield for the year ended December 31, 2013 3		2.74		%	2.87		%		1.79		%		2.77		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.4 billion and the weighted average contractual interest we are entitled to receive was 5.50% of this amount as of December 31, 2013. The par value of our principal-only agency MBS strips was $271 million as of December 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 December 31, 2013.
	3	Incorporates a weighted average future constant prepayment rate assumption of 7% based on forward rates as of December 31, 2013.
			December 31, 2013
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	64,057		$	242			$	(1,338	)		$	62,961
Adjustable rate		1,223			15				(3		)		1,235
CMO		1,313			3				(8		)		1,308
Interest-only and principal-only strips		432			16				(11		)		437
Total agency MBS		$	67,025		$	276			$	(1,360	)		$	65,941
The actual maturities of our agency MBS 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, 2014 and December 31, 2013, our weighted average expected constant prepayment rate ("CPR") over the remaining life of our aggregate agency MBS portfolio was 8% and 7%, 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, 2014 and December 31, 2013 according to their estimated weighted average life classification (dollars in millions):
		31-Mar-14											December 31, 2013
Estimated Weighted Average Life of Agency MBS Classified as Available-for-Sale 1		Fair Value			Amortized				Weighted		Weighted		Fair Value			Amortized		Weighted		Weighted
					Cost				Average		Average					Cost		Average		Average
									Coupon		Yield							Coupon		Yield
≤ 1 year		$	27		$	25			2.49%		1.81%		$	129		$	129	3.07%		2.53%
> 1 year and ≤ 3 years		191			186				4.86%		3.29%		498			491		4.08%		2.25%
> 3 years and ≤ 5 years		22,947			22,758				3.55%		2.53%		24,471			24,342		3.59%		2.57%
> 5 years and ≤10 years		32,534			33,284				3.51%		2.80%		38,522			39,635		3.39%		2.73%
> 10 years		246			260				3.61%		2.87%		1,884			1,996		3.66%		2.96%
Total		$	55,945		$	56,513			3.53%		2.70%		$	65,504		$	66,593	3.47%		2.68%
_______________________
1	Excludes interest and principal-only strips.
The weighted average life of our interest-only strips was 6.2 and 6.3 years as of March 31, 2014 and December 31, 2013, respectively. The weighted average life of our principal-only strips was 8.3 and 8.6 years as of March 31, 2014 and December 31, 2013, 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, 2014 and 2013 (in millions):
Agency Securities Classified as		Beginning Accumulated OCI			Unrealized			Reversal of			Ending
Available-for-Sale		Balance			Gains and (Losses), Net			Unrealized			Accumulated OCI
								(Gains) and Losses,			Balance
								Net on Realization
Three months ended March 31, 2014		$	(1,087	)	502			19			$	(566	)
Three months ended March 31, 2013		$	2,040		(863	)		26			$	1,203
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, 2014 and December 31 and March 31, 2013 (in millions):
		Unrealized Loss Position For
		Less than 12 Months							12 Months or More							Total
Agency Securities Classified as		Estimated Fair			Unrealized				Estimated				Unrealized			Estimated Fair		Unrealized
Available-for-Sale		Value			Loss				Fair Value				Loss			Value		Loss
March 31, 2014		$	22,112		$	(442	)		$	8,673			$	(461	)	$	30,785	$	(903	)
December 31, 2013		$	42,853		$	(1,248	)		$	1,586			$	(101	)	$	44,439	$	(1,349	)
March 31, 2013		$	25,963		$	(174	)		$	84			$	(2	)	$	26,047	$	(176	)
As of March 31, 2014 and 2013, a decision had not been made 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 GSE guarantees, but are rather due to changes in interest rates and prepayment expectations. Accordingly, we did not recognize any OTTI charges on our investment securities for the three months ended March 31, 2014 and 2013. However, as we continue to actively manage our portfolio, we may recognize additional realized losses on our agency securities upon selecting specific securities to sell.
Gains and Losses
The following table is a summary of our net gain (loss) from the sale of agency securities classified as available-for-sale for the three months ended March 31, 2014 and 2013 (in millions):
		Three Months Ended
Agency Securities Classified as		31-Mar-14			March 31, 2013
Available-for-Sale
Agency MBS sold, at cost		$	(9,711	)	$	(20,328	)
Proceeds from agency MBS sold 1		9,692			20,302
Net loss on sale of agency MBS		$	(19	)	$	(26	)
Gross gain on sale of agency MBS		$	42		$	87
Gross loss on sale of agency MBS		(61		)	(113		)
Net loss on sale of agency MBS		$	(19	)	$	(26	)
________________________
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, 2014 and 2013, we recognized a net unrealized gain of $12 million and a net unrealized loss of $1 million, respectively, for the change in value of investments in interest and principal-only strips in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. Over the same periods, we did not recognize any realized gains or losses on our interest or principal-only securities.
Securitizations and Variable Interest Entities
As of March 31, 2014 and December 31, 2013, we held investments in CMO trusts, which are 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.
In connection with our consolidated CMO trusts, we recognized agency securities with a total fair value of $1.4 billion and $1.5 billion as of March 31, 2014 and December 31, 2013, respectively, and debt, at fair value, of $874 million and $910 million, respectively, in our accompanying consolidated balance sheets. As of March 31, 2014 and December 31, 2013, 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 $863 million and $900 million, respectively. We re-measure our consolidated debt at fair value through earnings in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. For the three months ended March 31, 2014 and 2013, we recognized a net loss of $(3) million and a net gain of $13 million in earnings, respectively, associated with our consolidated debt. 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.
As of March 31, 2014 and December 31, 2013, the fair value of our CMO securities and interest and principal-only securities was $1.7 billion, excluding the consolidated CMO trusts discussed above, or $2.3 billion including the net asset value of our consolidated CMO trusts. Our maximum exposure to loss related to our CMO securities and interest and principal-only securities, including our consolidated CMO trusts, was $265 million and $246 million as of March 31, 2014 and December 31, 2013, respectively.

Repurchase_Agreements_And_Othe

Repurchase Agreements And Other Debt	3 Months Ended
	Mar. 31, 2014
Disclosure of Repurchase Agreements [Abstract]	'
Repurchase Agreements And Other Debt	'
	Repurchase Agreements and Other Debt
	We pledge certain of our securities as collateral under repurchase arrangements with financial institutions, the terms and conditions of which are negotiated on a transaction-by-transaction basis (see Note 7). 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. If the fair value of our pledged securities declines, lenders will typically require us to post additional collateral or pay down borrowings to re-establish agreed upon collateral requirements, referred to as "margin calls." Similarly, if the fair value of our pledged securities increases, lenders may release collateral back to us. As of March 31, 2014, we have met all margin call requirements.
	The following table summarizes our borrowings under repurchase arrangements and weighted average interest rates classified by remaining maturities as of March 31, 2014 and December 31, 2013 (dollars in millions):
		31-Mar-14					December 31, 2013
	Remaining Maturity	Repurchase Agreements		Weighted		Weighted	Repurchase Agreements		Weighted		Weighted
				Average		Average Days			Average		Average Days
				Interest		to Maturity			Interest		to Maturity
				Rate					Rate
	Agency MBS:
	≤ 1 month	$	13,440	0.37	%	15	$	23,577	0.42	%	15
	> 1 to ≤ 3 months	17,396		0.38	%	54	20,490		0.43	%	61
	> 3 to ≤ 6 months	5,242		0.45	%	137	6,946		0.45	%	140
	> 6 to ≤ 9 months	4,560		0.51	%	232	2,232		0.53	%	230
	> 9 to ≤ 12 months	4,171		0.49	%	326	3,607		0.54	%	323
	> 12 to ≤ 24 months	3,232		0.57	%	517	3,261		0.6	%	603
	> 24 to ≤ 36 months	540		0.61	%	876	500		0.62	%	930
	> 36 months	999		0.66	%	1,599	602		0.68	%	1,468
	Total agency MBS	49,580		0.43	%	162	61,215		0.45	%	124
	U.S. Treasury securities:
	1 day	149		0.05	%	1	2,318		0.02	%	1
	Total / Weighted Average	$	49,729	0.43	%	161	$	63,533	0.44	%	119
	As of March 31, 2014 and December 31, 2013, debt of consolidated VIEs, at fair value ("other debt") was $874 million and $910 million, respectively. As of March 31, 2014 and December 31, 2013, our other debt had a weighted average interest rate of LIBOR plus 43 and 42 basis points and a principal balance of $863 million and $900 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, 2014 was 6.5 years.
	As of March 31, 2014 and December 31, 2013, we also had outstanding forward commitments to purchase and sell agency securities through the TBA market (see Notes 3 and 6). These transactions, also referred to as TBA dollar roll transactions, represent a form of off-balance sheet financing and serve to either increase, in the case of forward purchases, or decrease, in the case of forward sales, our "at risk" leverage. However, pursuant to ASC 815, we typically account for such transactions as one or more series of derivative transactions and, consequently, they are not included in our on-balance sheet debt or measurement of commensurate leverage ratios.

Derivative_and_Other_Hedging_I

Derivative and Other Hedging Instruments	3 Months Ended
	Mar. 31, 2014
Derivative Asset, Fair Value, Amount Not Offset Against Collateral [Abstract]	'
Derivative and Other Hedging Instruments	'
	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 typically enter into agreements for interest rate swaps and interest rate swaptions. 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 and principal-only securities. 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, 2014 and 2013, we reclassified $43 million and $49 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 for these periods were $126 million and $133 million, respectively. The difference of $83 million and $84 million for these periods, respectively, is reported in our accompanying consolidated statements of comprehensive income in gain (loss) on derivative instruments and other securities, net. As of March 31, 2014, the remaining net deferred loss in accumulated OCI related to de-designated interest rate swaps was $253 million and will be reclassified from OCI into interest expense over a remaining weighted average period of 1.9 years. As of March 31, 2014, the net deferred loss expected to be reclassified from OCI into interest expense over the next twelve months was $143 million.
	Derivative Assets (Liabilities), at Fair Value
	The table below summarizes fair value information about our derivative assets and liabilities as of March 31, 2014 and December 31, 2013 (in millions):
	Derivatives Instruments		Balance Sheet Location		March 31, 2014				December 31, 2013
	Interest rate swaps		Derivative assets, at fair value		$	560			$	880
	Swaptions		Derivative assets, at fair value		96				258
	TBA securities		Derivative assets, at fair value		24				17
	U.S. Treasury futures - short		Derivative assets, at fair value		6				39
					$	686			$	1,194
	Interest rate swaps		Derivative liabilities, at fair value		$	(368	)		$	(400	)
	TBA securities		Derivative liabilities, at fair value		(49		)		(22		)
					$	(417	)		$	(422	)
	Additionally, as of March 31, 2014 and December 31, 2013, 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 $6.7 billion and $1.8 billion, respectively. The borrowed securities were used to cover short sales of U.S. Treasury securities from which we received total proceeds of $6.7 billion and $1.9 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, 2014 and December 31, 2013 (dollars in millions):
			31-Mar-14
	Payer Interest Rate Swaps		Notional				Average			Average			Net				Average
			Amount 1				Fixed			Receive			Estimated				Maturity
							Pay Rate 2			Rate 3			Fair Value				(Years) 4
	≤ 3 years		$	16,650			1.55	%		0.18	%		$	(327	)		1.4
	> 3 to ≤ 5 years		10,575				1.29	%		0.24	%		78				4
	> 5 to ≤ 7 years		6,250				2.09	%		0.25	%		66				5.9
	> 7 to ≤ 10 years		10,175				2.51	%		0.24	%		287				8.5
	> 10 years		2,750				3.17	%		0.24	%		88				14.1
	Total Payer Interest Rate Swaps		$	46,400			1.87	%		0.21	%		$	192			4.9
	________________________
	1	Notional amount includes forward starting swaps of $9.5 billion with an average forward start date of 1.9 years from March 31, 2014.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.57% as of March 31, 2014.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from March 31, 2014 through stated maturity date.
			December 31, 2013
	Payer Interest Rate Swaps 1		Notional				Average		Average		Net				Average
			Amount				Fixed		Receive		Estimated				Maturity
							Pay Rate		Rate		Fair Value				(Years)
	≤ 3 years		$	16,750			1.57%		0.19%		$	(382	)		1.6
	> 3 to ≤ 5 years		10,225				1.07%		0.24%		81				3.9
	> 5 to ≤ 7 years		5,700				1.97%		0.26%		113				6
	> 7 to ≤ 10 years		8,825				2.28%		0.24%		499				8.8
	> 10 years		1,750				2.79%		0.24%		169				14.7
	Total Payer Interest Rate Swaps		$	43,250			1.70%		0.22%		$	480			4.7
	________________________
	1	Notional amount includes forward starting swaps of $4.0 billion with an average forward start date of 1.9 years from December 31, 2013.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.57% as of December 31, 2013.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from December 31, 2013 through stated maturity date.
	The following tables summarize our interest rate swaption agreements outstanding as of March 31, 2014 and December 31, 2013 (dollars in millions):
			March 31, 2014
			Option										Underlying Payer Swap
	Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Pay		Average		Average
							Value				Months to		Amount				Rate		Receive		Term
											Expiration								Rate		(Years)
																			(LIBOR)
	Payer Swaptions
	≤ 1 year		$	111			$	44			5		$	4,650			2.98%		3M		6.4
	> 1 to ≤ 2 years		60				34				18		2,450				3.55%		3M		4.5
	> 2 to ≤ 3 years		23				15				28		900				3.99%		3M		5.4
	Total Payer Swaptions		$	194			$	93			12		$	8,000			3.27%		3M		5.7
			March 31, 2014
			Option										Underlying Receiver Swap
			Cost				Fair				Average		Notional				Average Fixed Receive		Average		Average
							Value				Months to		Amount				Rate		Pay		Term
											Expiration								Rate		(Years)
													(LIBOR)
Receiver Swaption		$	3			$	3			12		$	1,000			2.26%		3M		10
		December 31, 2013
		Option										Underlying Payer Swap
Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Pay		Average		Average
						Value				Months to		Amount				Rate		Receive		Term
										Expiration								Rate		(Years)
																		(LIBOR)
Payer Swaptions
≤ 1 year		$	193			$	117			4		$	9,400			2.87%		3M		7.8
> 1 to ≤ 2 years		105				92				19		3,600				3.40%		3M		5.6
> 2 to ≤ 3 years		35				45				30		1,150				3.81%		3M		5.8
> 3 to ≤ 5 years		2				4				52		100				4.80%		3M		7
Total Payer Swaptions		$	335			$	258			10		$	14,250			3.09%		3M		7
We did not have any receiver swaptions as of December 31, 2013.
The following table summarizes our contracts to purchase and sell TBA contracts as of March 31, 2014 and December 31, 2013 (in millions):
		31-Mar-14																December 31, 2013
Purchase and Sale Contracts for TBAs		Notional				Cost Basis 2				Market Value 3				Net Carrying Value 4				Notional			Cost Basis 2			Market Value 3			Net Carrying Value 4
		Amount 1																Amount 1
TBA securities:
Purchase contracts		$	17,699			$	18,136			$	18,095			$	(41	)		$	6,660		$	6,882		$	6,864		$	(18	)
Sale contracts		(3,790		)		(4,009		)		(3,993		)		16				(4,541		)	(4,606		)	(4,593		)	13
TBA securities, net 5		$	13,909			$	14,127			$	14,102			$	(25	)		$	2,119		$	2,276		$	2,271		$	(5	)
________________________
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 / (received) 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 and the cost basis of the TBA contract as of period-end 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
Gain (Loss) From Derivative Instruments and Other Securities, Net
The tables below summarize the effect of our derivative and other hedging instruments on our consolidated statements of comprehensive income for the three months ended March 31, 2014 and 2013 (in millions):
		Three Months Ended March 31, 2014
Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount				Amount of
		Long/(Short)							Expiration or			Long/(Short) March 31, 2014				Gain/(Loss)
		31-Dec-13							Exercise							Recognized in
																Income on
																Derivatives 1
Net TBA securities		$	2,119			24,376			(12,586	)		$	13,909			$	60
Interest rate swaps		$	(43,250	)		(5,900	)		2,750			$	(46,400	)		(380		)
Payer swaptions, net		$	(14,250	)		(1,000	)		7,250			$	(8,000	)		(105		)
Receiver swaption		$	—			1,000			—			$	1,000			—
U.S. Treasury securities - short position		$	(2,007	)		(7,241	)		2,462			$	(6,786	)		(45		)
U.S. Treasury securities - long position		$	3,927			1,900			(5,627	)		$	200			72
U.S. Treasury futures contracts - short position		$	(1,730	)		(730	)		1,730			$	(730	)		(36		)
TBA put option		$	—			(50	)		50			$	—			—
																$	(434	)
________________________________
1	Excludes a net gain of $49 million from investments in REIT equity securities, a net loss of $3 million from debt of consolidated VIEs, a net gain of$12 million on interest and principal-only securities and other miscellaneous net losses of $2 million recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
		Three Months Ended March 31, 2013
Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount Long/(Short) March 31, 2013				Amount of
		Long/(Short)							Expiration or							Gain/(Loss)
		31-Dec-12							Exercise							Recognized in
																Income on
																Derivatives 1
Net TBA and forward settling agency securities		$	12,477			43,267			(29,476	)		$	26,268			$	(102	)
Interest rate swaps		$	(46,850	)		(5,750	)		1,350			$	(51,250	)		54
Payer swaptions		$	(14,450	)		(11,150	)		2,700			$	(22,900	)		(44		)
U.S. Treasury securities - short position		$	(11,835	)		(9,935	)		9,210			$	(12,560	)		(3		)
U.S. Treasury futures contracts - short position		$	—			(800	)		—			$	(800	)		(15		)
																$	(110	)
______________________
1	Excludes a net loss of $1 million on interest and principal-only securities and a net gain of $13 million from debt of consolidated VIEs recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.

Pledged_Assets_Notes

Pledged Assets (Notes)	3 Months Ended
	Mar. 31, 2014
Offsetting Assets and Liabilities [Abstract]	'
Pledged Assets [Text Block]	'
	Pledged Assets
	Our repurchase agreements and derivative contracts require us to fully collateralize our obligations under the agreements based upon our counterparties' collateral requirements and their determination of the fair value of the securities pledged as collateral, which fluctuates with changes in interest rates, credit quality and liquidity conditions within the investment banking, mortgage finance and real estate industries. In addition, obligations under our derivative agreements will typically vary over time based on similar factors as well as the remaining term of the derivative contract. We are also typically required to post initial collateral upon execution of derivative transactions, such as interest rate swaps and TBA contracts. If we breach any of these provisions, we will be required to fully settle our obligations under the agreements, which could include a forced liquidation of our pledged collateral.
	Our repurchase agreement and derivative counterparties also apply a "haircut" to our pledged collateral, which means our collateral is valued at slightly less than market value and limits the amount we can borrow against our securities. This haircut reflects the underlying risk of the specific collateral and protects our counterparty against a change in its value. Our agreements do not specify the haircut; rather haircuts are determined on an individual transaction basis.
	Consequently, the use of repurchase agreements and derivative instruments exposes us to credit risk relating to potential losses that could be recognized in the event that our counterparties fail to perform their obligations under such agreements. We minimize this risk by limiting our repurchase agreement and derivative counterparties to major financial institutions with acceptable credit ratings or to a registered clearinghouse, and we monitor our positions with individual counterparties. In the event of a default by a counterparty we may have difficulty obtaining our assets pledged as collateral to such counterparty and may not receive payments provided for under the terms of our derivative agreements. In the case of centrally cleared instruments, we could be exposed to credit risk if the central clearing agency or a clearing member defaults on its respective obligation to perform under the contract. However, we believe that the risk is minimal due to clearing exchange initial and daily mark to market margin requirements and clearinghouse guarantee funds and other resources that are available in the event of a clearing member default.
	Further, each of our International Swaps and Derivatives Association ("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. Additionally, under certain of our ISDA Master Agreements, we could be required to settle our obligations under the agreements if we fail to maintain certain minimum stockholders' 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, 2014, the fair value of additional collateral that could be required to be posted as a result of the credit-risk-related contingent features being triggered was not material to our financial statements.
	As of March 31, 2014, our amount at risk with any counterparty related to our repurchase agreements was less than 4% of our stockholders' equity and our amount at risk with any counterparty related to our interest rate swap and swaption agreements, excluding centrally cleared swaps, was less than 1% of our stockholders' equity.
	Assets Pledged to Counterparties
	The following tables summarize our assets pledged as collateral under our 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, 2014 and December 31, 2013 (in millions):
			March 31, 2014
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	52,047	$	1,417	$	56	$	519		$	54,039
	U.S. Treasury securities - fair value		125		—		71		—			196
	Accrued interest on pledged securities		146		4		—		1			151
	Restricted cash		1		—		224		44			269
	Total		$	52,319	$	1,421	$	351	$	564		$	54,655
			December 31, 2013
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	62,708	$	1,459	$	28	$	91		$	64,286
	U.S. Treasury securities - fair value		3,708		—		70		—			3,778
	Accrued interest on pledged securities		189		5		1		—			195
	Restricted cash		3		—		41		57			101
	Total		$	66,608	$	1,464	$	140	$	148		$	68,360
	The cash and cash equivalents and agency securities pledged as collateral under our derivative agreements are included in restricted cash and agency securities, at fair value, respectively, on our consolidated balance sheets.
	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, 2014 and 2013 (in millions):
			March 31, 2014						December 31, 2013
	Agency Securities Pledged by Remaining Maturity of Repurchase Agreements and Debt of Consolidated VIEs		Fair Value of Pledged Securities		Amortized		Accrued		Fair Value of Pledged Securities			Amortized			Accrued
					Cost of Pledged Securities		Interest on					Cost of Pledged Securities			Interest on
							Pledged								Pledged
							Securities								Securities
	Agency MBS:
	≤ 30 days		$	17,683	$	17,858	$	49	$	27,694		$	28,125		$	76
	> 30 and ≤ 60 days		15,881		16,024		44		14,955			15,210			42
	> 60 and ≤ 90 days		5,585		5,630		16		10,117			10,290			28
	> 90 days		14,315		14,519		41		11,401			11,623			32
	Total agency MBS		53,464		54,031		150		64,167			65,248			178
	U.S. Treasury securities:
	1 day		125		125		—		3,708			3,760			16
	Total		$	53,589	$	54,156	$	150	$	67,875		$	69,008		$	194
	As of March 31, 2014 and December 31, 2013, none of our repurchase agreement borrowings backed by agency MBS were due on demand or mature overnight.
	Assets Pledged from Counterparties
	As of March 31, 2014 and December 31, 2013, we also had assets pledged to us as collateral under our repurchase, reverse repurchase and derivative agreements summarized in the tables below (in millions).
			31-Mar-14
	Assets Pledged to AGNC		Repurchase Agreements		Reverse Repurchase Agreements		Derivative Agreements		Total
	Agency MBS - fair value		$	—	$	—	$	17	$	17
	U.S. Treasury securities - fair value		—		6,658		56		6,714
	Cash		16		—		167		183
	Total		$	16	$	6,658	$	240	$	6,914
			31-Dec-13
	Assets Pledged to AGNC		Repurchase Agreements		Reverse Repurchase Agreements		Derivative Agreements		Total
	Agency MBS - fair value		$	—	$	—	$	82	$	82
	U.S. Treasury securities - fair value		—		1,848		164		2,012
	Cash		—		—		366		366
	Total		$	—	$	1,848	$	612	$	2,460
	U.S Treasury securities received as collateral under our reverse repurchase agreements are accounted for as securities borrowing transactions and are used to cover short sales of the same securities. We recognize a corresponding obligation to return the borrowed securities at fair value on the accompanying consolidated balance sheets based on the value of the underlying borrowed securities as of the reporting date.
	Cash collateral received is recognized in cash and cash equivalents with a corresponding amount recognized in accounts payable and other accrued liabilities on the accompanying consolidated balance sheets.
	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, 2014 and December 31, 2013 (in millions):
			Offsetting of Financial Assets and Derivative Assets
			Gross Amounts of Recognized Assets		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Assets Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset						Net Amount
									in the
									Consolidated Balance Sheets
									Financial Instruments			Collateral Received 2
31-Mar-14
Interest rate swap and swaption agreements, at fair value 1		$	656	$	—	$	656	$	(287	)	$	(240	)	$	129
Receivable under reverse repurchase agreements		6,685		—		6,685		(4,773		)	(1,912		)	—
Total derivative, other hedging instruments and other assets		$	7,341	$	—	$	7,341	$	(5,060	)	$	(2,152	)	$	129
31-Dec-13
Interest rate swap and swaption agreements, at fair value 1		$	1,138	$	—	$	1,138	$	(331	)	$	(610	)	$	197
Receivable under reverse repurchase agreements		1,881		—		1,881		(1,881		)	—			—
Total derivative, other hedging instruments and other assets		$	3,019	$	—	$	3,019	$	(2,212	)	$	(610	)	$	197
		Offsetting of Financial Liabilities and Derivative Liabilities
		Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset						Net Amount
								in the
								Consolidated Balance Sheets
								Financial Instruments			Collateral Pledged 2
31-Mar-14
Interest rate swap agreements, at fair value 1		$	368	$	—	$	368	$	(288	)	$	(80	)	$	—
Repurchase agreements		49,729		—		49,729		(4,773		)	(44,806		)	150
Total derivative, other hedging instruments and other liabilities		$	50,097	$	—	$	50,097	$	(5,061	)	$	(44,886	)	$	150
31-Dec-13
Interest rate swap agreements, at fair value 1		$	400	$	—	$	400	$	(331	)	$	(69	)	$	—
Repurchase agreements		63,533		—		63,533		(1,881		)	(61,652		)	—
Total derivative, other hedging instruments and other liabilities		$	63,933	$	—	$	63,933	$	(2,212	)	$	(61,721	)	$	—
_______________________
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 [Text Block]	'
			Offsetting of Financial Liabilities and Derivative Liabilities
			Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset						Net Amount
									in the
									Consolidated Balance Sheets
									Financial Instruments			Collateral Pledged 2
	31-Mar-14
	Interest rate swap agreements, at fair value 1		$	368	$	—	$	368	$	(288	)	$	(80	)	$	—
	Repurchase agreements		49,729		—		49,729		(4,773		)	(44,806		)	150
	Total derivative, other hedging instruments and other liabilities		$	50,097	$	—	$	50,097	$	(5,061	)	$	(44,886	)	$	150
	31-Dec-13
	Interest rate swap agreements, at fair value 1		$	400	$	—	$	400	$	(331	)	$	(69	)	$	—
	Repurchase agreements		63,533		—		63,533		(1,881		)	(61,652		)	—
	Total derivative, other hedging instruments and other liabilities		$	63,933	$	—	$	63,933	$	(2,212	)	$	(61,721	)	$	—
	_______________________
	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.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2014
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, 2014. 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, 2014 and December 31, 2013 (dollars in millions):
		Fair Value Hierarchy
		Level 1		Level 2		Level 3
	March 31, 2014
	Assets:
	Agency securities	$	—	$	56,377	$	—
	U.S. Treasury securities	196		—		—
	Interest rate swaps	—		560		—
	Payer swaptions	—		96		—
	REIT equity securities	352		—
	U.S. Treasury futures	6		—		—
	TBA securities	—		24		—
	Total	$	554	$	57,057	$	—
	Liabilities:
	Debt of consolidated VIEs	$	—	$	874	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	6,658		—		—
	Interest rate swaps	—		368		—
	TBA securities	—		49		—
	Total	$	6,658	$	1,291	$	—
	December 31, 2013
	Assets:
	Agency securities	$	—	$	65,941	$	—
	U.S. Treasury securities	3,822		—		—
	Interest rate swaps	—		880		—
	Payer swaptions	—		258		—
	REIT equity securities	237		—		—
	U.S. Treasury futures	39		—		—
	TBA securities	—		17		—
	Total	$	4,098	$	67,096	$	—
	Liabilities:
	Debt of consolidated VIEs	$	—	$	910	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	1,848		—		—
	Interest rate swaps	—		400		—
	TBA securities	—		22		—
	Total	$	1,848	$	1,332	$	—
	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.

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2014
Stockholders' Equity Note [Abstract]	'
Stockholders' Equity	'
	Stockholders' Equity
	Common Stock Repurchase Program
	In October 2012, our Board of Directors adopted a program that provides for stock repurchases of up to $500 million of our outstanding shares of common stock through December 31, 2013.  In September 2013, our Board of Directors increased the authorized amount to $1 billion of our outstanding shares of common stock and extended its authorization through December 31, 2014. In January 2014, our Board of Directors increased the authorized amount by an additional $1 billion of our outstanding shares of common stock through December 31, 2014. 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 Exchange Act of 1934, as amended.  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 Rule 10b-18, which sets certain restrictions on the method, timing, price and volume of stock repurchases.
	During the three months ended March 31, 2014, we repurchased approximately 3.4 million shares of our common stock at an average repurchase price of $22.10 per share, including expenses, totaling $74 million. As of March 31, 2014, the total remaining amount authorized for repurchases of our common stock was $992 million.
	Accumulated Other Comprehensive Income (Loss)
	The following table summarizes changes to accumulated OCI for the three months ended March 31, 2014 and 2013 (in millions):
	Accumulated Other Comprehensive (Loss) Income	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated OCI
								Balance
	Balance as of December 31, 2013	$	(1,087	)	$	(296	)	$	(1,383	)
	OCI before reclassifications	502			—			502
	Amounts reclassified from accumulated OCI	19			43			62
	Balance as of March 31, 2014	$	(566	)	$	(253	)	$	(819	)
	Balance as of December 31, 2012	$	2,040		$	(485	)	$	1,555
	OCI before reclassifications	(863		)	—			(863		)
	Amounts reclassified from accumulated OCI	26			49			75
	Balance as of March 31, 2013	$	1,203		$	(436	)	$	767
	The following table summarizes reclassifications out of accumulated OCI for the three months ended March 31, 2014 and 2013 (in millions):
		Three Months Ended March 31,						Line Item in the Consolidated
								Statements of Comprehensive Income
	Amounts Reclassified from Accumulated OCI	2014			2013			Where Net Income is Presented
	Loss amounts reclassified from accumulated OCI for available-for-sale MBS	$	19		$	26		Gain (loss) on sale of agency securities, net
	Periodic interest costs of interest rate swaps previously designated as hedges under GAAP, net	43			49			Interest expense
	Total reclassifications	$	62		$	75

Subsequent_Event_Notes

Subsequent Event (Notes)	3 Months Ended
	Mar. 31, 2014
Subsequent Events [Abstract]	'
Subsequent Events [Text Block]	'
	Subsequent Event
	On May 8, 2014, we completed a public offering in which 7.0 million depository shares with a liquidation preference of $25.00 per depositary share were sold to the underwriters at a price of $24.2125 per depository share, for proceeds, net of offering expenses, of approximately $169 million. Each depositary share represents a 1/1,000th interest in a share of our 7.750% Series B Cumulative Redeemable Preferred Stock ("Series B Preferred Stock"). In connection with the offering, we granted the underwriters an option for 30 days to purchase up to an additional 1.05 million depositary shares to cover overallotments, if any. Our Series B Preferred Stock has no stated maturity, is not subject to any sinking fund or mandatory redemption and ranks on parity with our 8.000% Series A Cumulative Redeemable Preferred Stock. Under certain circumstances upon a change of control, our Series B Preferred Stock is convertible to shares of our common stock. Holders of depositary shares have no voting rights, except under limited conditions, and are entitled to receive cumulative cash dividends at a rate of 7.750% per annum of the $25.00 per depository share liquidation preference before holders of our common stock are entitled to receive any dividends. Dividends are payable quarterly in arrears on the 15th day of each January, April, July and October. Depositary shares are redeemable at $25.00 per depository share plus accumulated and unpaid dividends (whether or not declared) exclusively at our option commencing on May 8, 2019, or earlier under certain circumstances intended to preserve our qualification as a REIT for federal income tax purposes.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2014
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 sell any of our agency securities as part of our overall management of our investment portfolio. Accordingly, we typically designate our agency 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 (loss) ("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 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 and principal-only securities are included in agency securities, at fair value on the accompanying consolidated balance sheets.
	REIT equity securities represent investments in the common stock of other publicly traded mortgage REITs that invest predominantly in agency MBS. We designate our investments in REIT equity securities as trading securities and report them at fair value on the accompanying consolidated balance sheets.
	We estimate the fair value of our agency 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, benchmark 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. We estimate the fair value of our REIT equity securities on a market approach using "Level 1" inputs based on quoted market prices. Refer to Note 8 for further discussion of fair value measurements.
	We evaluate our agency securities for other-than-temporary impairment ("OTTI") on at least a quarterly basis. The determination of whether a security is other-than-temporarily impaired may involve judgments and assumptions based on subjective and objective factors. When a security is impaired, an OTTI is considered to have occurred if any one of the following three conditions exist as of the financial reporting date: (i) we intend to sell the security (that is, a decision has been made to sell the security), (ii) it is more likely than not that we will be required to sell the security before recovery of its amortized cost basis or (iii) we do not expect to recover the security's amortized cost basis, even if we do not intend to sell the security and it is not more likely than not that we will be required to sell the security. A general allowance for unidentified impairments in a portfolio of securities is not permitted.
	If either of the first two conditions exists as of the financial reporting date, 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. If the third condition exists, the OTTI is separated into (i) the amount relating to credit loss (the "credit component") and (ii) the amount relating to all other factors (the "non-credit components"). Only the credit component is recognized in earnings, with the non-credit components recognized in OCI. However, in evaluating if the third condition exists, our investments in agency securities typically would not have a credit component since the principal and interest are guaranteed by a GSE and, therefore, any unrealized loss is not the result of a credit loss. In addition, since we designate our agency securities as available-for-sale securities with unrealized gains and losses recognized in OCI, any impairment loss for non-credit components is already recognized in OCI.
	The liquidity of the agency securities market allows us to obtain competitive bids and execute on a sale transaction typically within a day of making the decision to sell a security and, therefore, we generally do not make decisions to sell specific agency securities until shortly prior to initiating a sell order. In some instances, we may sell specific agency securities by delivering such securities into existing short to-be-announced ("TBA") contracts. TBA market conventions require the identification of the specific securities to be delivered no later than 48 hours prior to settlement. If we settle a short TBA contract through the delivery of securities, we will generally identify the specific securities to be delivered within one to two days of the 48-hour deadline.
Interest Income	'
	Interest Income
	Interest income is accrued based on the outstanding principal amount of the investment securities and their contractual terms. Premiums or discounts associated with the purchase of investment securities are amortized or accreted into interest income, respectively, 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 its 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) the actual prepayments to date plus our currently 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.
Derivative and other Hedging Instruments	'
	Derivative Instruments
	We use a variety of derivative instruments to 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 ("swaptions"). We also utilize forward contracts for the purchase or sale of agency MBS securities on a generic pool basis, or a TBA contract, 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 and principal-only securities.
	We may also enter into TBA contracts as a means of investing in and financing agency securities (thereby increasing our "at risk" leverage) or as a means of disposing of or reducing our exposure to agency securities (thereby reducing our "at risk" leverage). Pursuant to TBA contracts, we agree to purchase or sell, 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 or long position (referred to as a "pair off"), net settling the paired off positions for cash, and simultaneously purchasing or selling a similar TBA contract for a later settlement date. This transaction is commonly referred to as a "dollar roll." The agency securities purchased or sold 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/loss." 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 the 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 September 30, 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 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 swaps") with terms up to 20 years. The floating rate we receive under our swap agreements has the effect of offsetting the repricing characteristics of our repurchase agreements and cash flows on such liabilities. Our swap agreements are privately negotiated in the over−the−counter ("OTC") market and may be centrally cleared through a registered commodities exchange ("centrally cleared swaps").
	We estimate the fair value of our centrally cleared interest rate swaps using the daily settlement price determined by the respective exchange. Centrally cleared swaps are valued by the exchange using a pricing model that references the underlying rates including the overnight index swap rate and LIBOR forward rate to produce the daily settlement price.
	We estimate the fair value of our "non-centrally cleared" 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 the 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 statements 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.
	Our interest rate swaption agreements are privately negotiated in the OTC market and are not subject to central clearing. 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 may 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 or disposing of 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 either the TBA contracts do not settle in the shortest period of time possible or 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.
	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 and U.S. Treasury futures contracts 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 September 30, 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.

Investment_Securities_Tables

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2014
Available-for-sale Securities [Abstract]	'
Agency Securities [Table Text Block]	'
	The following tables summarize our investments in agency MBS as of March 31, 2014 (dollars in millions):
			31-Mar-14
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	42,131		$	11,730			$	209			$	54,070
	Unamortized discount		(17		)	(6		)		—				(23		)
	Unamortized premium		1,887			573				6				2,466
	Amortized cost		44,001			12,297				215				56,513
	Gross unrealized gains		238			93				4				335
	Gross unrealized losses		(646		)	(257		)		—				(903		)
	Total available-for-sale agency MBS, at fair value		43,593			12,133				219				55,945
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		386			29				—				415
	Gross unrealized gains		20			4				—				24
	Gross unrealized losses		(6		)	(1		)		—				(7		)
	Total agency MBS remeasured at fair value through earnings		400			32				—				432
	Total agency MBS, at fair value		$	43,993		$	12,165			$	219			$	56,377
	Weighted average coupon as of March 31, 2014 2		3.62		%	3.75		%		3.54		%		3.65		%
	Weighted average yield as of March 31, 2014 3		2.7		%	2.82		%		1.66		%		2.72		%
	Weighted average yield for the quarter ended March 31, 2014 3		2.53		%	2.61		%		1.67		%		2.54		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.3 billion and the weighted average contractual interest we are entitled to receive was 5.49% of this amount as of March 31, 2014. The par value of our principal-only agency MBS strips was $265 million as of March 31, 2014.
	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, 2014.
	3	Incorporates a weighted average future constant prepayment rate assumption of 8% based on forward rates as of March 31, 2014
	The following tables summarize our investments in agency MBS as of December 31, 2013 (dollars in millions):
			December 31, 2013
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	50,914		$	12,640			$	223			$	63,777
	Unamortized discount		(25		)	(7		)		—				(32		)
	Unamortized premium		2,210			631				7				2,848
	Amortized cost		53,099			13,264				230				66,593
	Gross unrealized gains		181			74				5				260
	Gross unrealized losses		(991		)	(358		)		—				(1,349		)
	Total available-for-sale agency MBS, at fair value		52,289			12,980				235				65,504
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		400			32				—				432
	Gross unrealized gains		13			3				—				16
	Gross unrealized losses		(9		)	(2		)		—				(11		)
	Total agency MBS remeasured at fair value through earnings		404			33				—				437
	Total agency MBS, at fair value		$	52,693		$	13,013			$	235			$	65,941
	Weighted average coupon as of December 31, 2013 2		3.53		%	3.78		%		3.56		%		3.58		%
	Weighted average yield as of December 31, 2013 3		2.66		%	2.87		%		1.66		%		2.7		%
	Weighted average yield for the year ended December 31, 2013 3		2.74		%	2.87		%		1.79		%		2.77		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.4 billion and the weighted average contractual interest we are entitled to receive was 5.50% of this amount as of December 31, 2013. The par value of our principal-only agency MBS strips was $271 million as of December 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 December 31, 2013.
	3	Incorporates a weighted average future constant prepayment rate assumption of 7% based on forward rates as of December 31, 2013.
			December 31, 2013
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	64,057		$	242			$	(1,338	)		$	62,961
	Adjustable rate		1,223			15				(3		)		1,235
	CMO		1,313			3				(8		)		1,308
	Interest-only and principal-only strips		432			16				(11		)		437
	Total agency MBS		$	67,025		$	276			$	(1,360	)		$	65,941
Components of Investment Securities [Table Text Block]	'
			31-Mar-14
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	54,056		$	307			$	(902	)		$	53,461
	Adjustable rate		1,176			19				—				1,195
	CMO		1,281			9				(1		)		1,289
	Interest-only and principal-only strips		415			24				(7		)		432
	Total agency MBS		$	56,928		$	359			$	(910	)		$	56,377
			December 31, 2013
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	64,057		$	242			$	(1,338	)		$	62,961
	Adjustable rate		1,223			15				(3		)		1,235
	CMO		1,313			3				(8		)		1,308
	Interest-only and principal-only strips		432			16				(11		)		437
	Total agency MBS		$	67,025		$	276			$	(1,360	)		$	65,941
Summary Of Agency Securities Estimated Weighted Average Life Classifications	'
	The following table summarizes our agency MBS classified as available-for-sale as of March 31, 2014 and December 31, 2013 according to their estimated weighted average life classification (dollars in millions):
			31-Mar-14											December 31, 2013
	Estimated Weighted Average Life of Agency MBS Classified as Available-for-Sale 1		Fair Value			Amortized				Weighted		Weighted		Fair Value			Amortized		Weighted		Weighted
						Cost				Average		Average					Cost		Average		Average
										Coupon		Yield							Coupon		Yield
	≤ 1 year		$	27		$	25			2.49%		1.81%		$	129		$	129	3.07%		2.53%
	> 1 year and ≤ 3 years		191			186				4.86%		3.29%		498			491		4.08%		2.25%
	> 3 years and ≤ 5 years		22,947			22,758				3.55%		2.53%		24,471			24,342		3.59%		2.57%
	> 5 years and ≤10 years		32,534			33,284				3.51%		2.80%		38,522			39,635		3.39%		2.73%
	> 10 years		246			260				3.61%		2.87%		1,884			1,996		3.66%		2.96%
	Total		$	55,945		$	56,513			3.53%		2.70%		$	65,504		$	66,593	3.47%		2.68%
	_______________________
	1	Excludes interest and principal-only strips.
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, 2014 and 2013 (in millions):
	Agency Securities Classified as		Beginning Accumulated OCI			Unrealized			Reversal of			Ending
	Available-for-Sale		Balance			Gains and (Losses), Net			Unrealized			Accumulated OCI
									(Gains) and Losses,			Balance
									Net on Realization
	Three months ended March 31, 2014		$	(1,087	)	502			19			$	(566	)
	Three months ended March 31, 2013		$	2,040		(863	)		26			$	1,203
Summary of Continuous Unrealized Loss Position of Available for Sale Securities [Table Text Block]	'
	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, 2014 and December 31 and March 31, 2013 (in millions):
			Unrealized Loss Position For
			Less than 12 Months							12 Months or More							Total
	Agency Securities Classified as		Estimated Fair			Unrealized				Estimated				Unrealized			Estimated Fair		Unrealized
	Available-for-Sale		Value			Loss				Fair Value				Loss			Value		Loss
	March 31, 2014		$	22,112		$	(442	)		$	8,673			$	(461	)	$	30,785	$	(903	)
	December 31, 2013		$	42,853		$	(1,248	)		$	1,586			$	(101	)	$	44,439	$	(1,349	)
	March 31, 2013		$	25,963		$	(174	)		$	84			$	(2	)	$	26,047	$	(176	)
Summary of Net Gain from Sale of Agency Securities [Table Text Block]	'
	The following table is a summary of our net gain (loss) from the sale of agency securities classified as available-for-sale for the three months ended March 31, 2014 and 2013 (in millions):
			Three Months Ended
	Agency Securities Classified as		31-Mar-14			March 31, 2013
	Available-for-Sale
	Agency MBS sold, at cost		$	(9,711	)	$	(20,328	)
	Proceeds from agency MBS sold 1		9,692			20,302
	Net loss on sale of agency MBS		$	(19	)	$	(26	)
	Gross gain on sale of agency MBS		$	42		$	87
	Gross loss on sale of agency MBS		(61		)	(113		)
	Net loss on sale of agency MBS		$	(19	)	$	(26	)
	________________________
	1	Proceeds include cash received during the period, plus receivable for agency MBS sold during the period as of period end.
Summary Of Agency Securities Pledged As Collateral Under Repurchase Agreements by Remaining Maturity	'
	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, 2014 and 2013 (in millions):
			March 31, 2014											December 31, 2013
	Agency Securities Pledged by Remaining Maturity of Repurchase Agreements and Debt of Consolidated VIEs		Fair Value of Pledged Securities			Amortized				Accrued				Fair Value of Pledged Securities			Amortized		Accrued
						Cost of Pledged Securities				Interest on							Cost of Pledged Securities		Interest on
										Pledged									Pledged
										Securities									Securities
	Agency MBS:
	≤ 30 days		$	17,683		$	17,858			$	49			$	27,694		$	28,125	$	76
	> 30 and ≤ 60 days		15,881			16,024				44				14,955			15,210		42
	> 60 and ≤ 90 days		5,585			5,630				16				10,117			10,290		28
	> 90 days		14,315			14,519				41				11,401			11,623		32
	Total agency MBS		53,464			54,031				150				64,167			65,248		178
	U.S. Treasury securities:
	1 day		125			125				—				3,708			3,760		16
	Total		$	53,589		$	54,156			$	150			$	67,875		$	69,008	$	194

Recovered_Sheet1

Repurchase Agreements and Other Debt (Tables)	3 Months Ended
	Mar. 31, 2014
Disclosure of Repurchase Agreements [Abstract]	'
Schedule of Borrowings under Repurchase Agreements and Weighted Average Interest Rates [Table Text Block]	'
	The following table summarizes our borrowings under repurchase arrangements and weighted average interest rates classified by remaining maturities as of March 31, 2014 and December 31, 2013 (dollars in millions):
		31-Mar-14					December 31, 2013
	Remaining Maturity	Repurchase Agreements		Weighted		Weighted	Repurchase Agreements		Weighted		Weighted
				Average		Average Days			Average		Average Days
				Interest		to Maturity			Interest		to Maturity
				Rate					Rate
	Agency MBS:
	≤ 1 month	$	13,440	0.37	%	15	$	23,577	0.42	%	15
	> 1 to ≤ 3 months	17,396		0.38	%	54	20,490		0.43	%	61
	> 3 to ≤ 6 months	5,242		0.45	%	137	6,946		0.45	%	140
	> 6 to ≤ 9 months	4,560		0.51	%	232	2,232		0.53	%	230
	> 9 to ≤ 12 months	4,171		0.49	%	326	3,607		0.54	%	323
	> 12 to ≤ 24 months	3,232		0.57	%	517	3,261		0.6	%	603
	> 24 to ≤ 36 months	540		0.61	%	876	500		0.62	%	930
	> 36 months	999		0.66	%	1,599	602		0.68	%	1,468
	Total agency MBS	49,580		0.43	%	162	61,215		0.45	%	124
	U.S. Treasury securities:
	1 day	149		0.05	%	1	2,318		0.02	%	1
	Total / Weighted Average	$	49,729	0.43	%	161	$	63,533	0.44	%	119

Derivative_and_Other_Hedging_I1

Derivative and Other Hedging Instruments (Tables)	3 Months Ended
	Mar. 31, 2014
Derivative [Line Items]	'
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, 2014 and December 31, 2013 (in millions):
	Derivatives Instruments		Balance Sheet Location		March 31, 2014				December 31, 2013
	Interest rate swaps		Derivative assets, at fair value		$	560			$	880
	Swaptions		Derivative assets, at fair value		96				258
	TBA securities		Derivative assets, at fair value		24				17
	U.S. Treasury futures - short		Derivative assets, at fair value		6				39
					$	686			$	1,194
	Interest rate swaps		Derivative liabilities, at fair value		$	(368	)		$	(400	)
	TBA securities		Derivative liabilities, at fair value		(49		)		(22		)
					$	(417	)		$	(422	)
Schedule of Interest Rate Swaption Agreements Outstandin [Table Text Block]	'
	The following tables summarize our interest rate swaption agreements outstanding as of March 31, 2014 and December 31, 2013 (dollars in millions):
			March 31, 2014
			Option										Underlying Payer Swap
	Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Pay		Average		Average
							Value				Months to		Amount				Rate		Receive		Term
											Expiration								Rate		(Years)
																			(LIBOR)
	Payer Swaptions
	≤ 1 year		$	111			$	44			5		$	4,650			2.98%		3M		6.4
	> 1 to ≤ 2 years		60				34				18		2,450				3.55%		3M		4.5
	> 2 to ≤ 3 years		23				15				28		900				3.99%		3M		5.4
	Total Payer Swaptions		$	194			$	93			12		$	8,000			3.27%		3M		5.7
			March 31, 2014
			Option										Underlying Receiver Swap
			Cost				Fair				Average		Notional				Average Fixed Receive		Average		Average
							Value				Months to		Amount				Rate		Pay		Term
											Expiration								Rate		(Years)
																			(LIBOR)
	Receiver Swaption		$	3			$	3			12		$	1,000			2.26%		3M		10
			December 31, 2013
			Option										Underlying Payer Swap
	Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Pay		Average		Average
							Value				Months to		Amount				Rate		Receive		Term
											Expiration								Rate		(Years)
																			(LIBOR)
	Payer Swaptions
	≤ 1 year		$	193			$	117			4		$	9,400			2.87%		3M		7.8
	> 1 to ≤ 2 years		105				92				19		3,600				3.40%		3M		5.6
	> 2 to ≤ 3 years		35				45				30		1,150				3.81%		3M		5.8
	> 3 to ≤ 5 years		2				4				52		100				4.80%		3M		7
	Total Payer Swaptions		$	335			$	258			10		$	14,250			3.09%		3M		7
Summary of Long and Short Position of Derivative Instruments	'
	The following table summarizes our contracts to purchase and sell TBA contracts as of March 31, 2014 and December 31, 2013 (in millions):
			31-Mar-14																December 31, 2013
	Purchase and Sale Contracts for TBAs		Notional				Cost Basis 2				Market Value 3				Net Carrying Value 4				Notional			Cost Basis 2			Market Value 3			Net Carrying Value 4
			Amount 1																Amount 1
	TBA securities:
	Purchase contracts		$	17,699			$	18,136			$	18,095			$	(41	)		$	6,660		$	6,882		$	6,864		$	(18	)
	Sale contracts		(3,790		)		(4,009		)		(3,993		)		16				(4,541		)	(4,606		)	(4,593		)	13
	TBA securities, net 5		$	13,909			$	14,127			$	14,102			$	(25	)		$	2,119		$	2,276		$	2,271		$	(5	)
	________________________
	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 / (received) 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 and the cost basis of the TBA contract as of period-end 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
Schedule Of Outstanding Not Designated As Hedging Instruments [Table Text Block]	'
			Three Months Ended March 31, 2013
	Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount Long/(Short) March 31, 2013				Amount of
			Long/(Short)							Expiration or							Gain/(Loss)
			31-Dec-12							Exercise							Recognized in
																	Income on
																	Derivatives 1
	Net TBA and forward settling agency securities		$	12,477			43,267			(29,476	)		$	26,268			$	(102	)
	Interest rate swaps		$	(46,850	)		(5,750	)		1,350			$	(51,250	)		54
	Payer swaptions		$	(14,450	)		(11,150	)		2,700			$	(22,900	)		(44		)
	U.S. Treasury securities - short position		$	(11,835	)		(9,935	)		9,210			$	(12,560	)		(3		)
	U.S. Treasury futures contracts - short position		$	—			(800	)		—			$	(800	)		(15		)
																	$	(110	)
	______________________
	1	Excludes a net loss of $1 million on interest and principal-only securities and a net gain of $13 million from debt of consolidated VIEs recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
	The tables below summarize the effect of our derivative and other hedging instruments on our consolidated statements of comprehensive income for the three months ended March 31, 2014 and 2013 (in millions):
			Three Months Ended March 31, 2014
	Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount				Amount of
			Long/(Short)							Expiration or			Long/(Short) March 31, 2014				Gain/(Loss)
			31-Dec-13							Exercise							Recognized in
																	Income on
																	Derivatives 1
	Net TBA securities		$	2,119			24,376			(12,586	)		$	13,909			$	60
	Interest rate swaps		$	(43,250	)		(5,900	)		2,750			$	(46,400	)		(380		)
	Payer swaptions, net		$	(14,250	)		(1,000	)		7,250			$	(8,000	)		(105		)
	Receiver swaption		$	—			1,000			—			$	1,000			—
	U.S. Treasury securities - short position		$	(2,007	)		(7,241	)		2,462			$	(6,786	)		(45		)
	U.S. Treasury securities - long position		$	3,927			1,900			(5,627	)		$	200			72
	U.S. Treasury futures contracts - short position		$	(1,730	)		(730	)		1,730			$	(730	)		(36		)
	TBA put option		$	—			(50	)		50			$	—			—
																	$	(434	)
	________________________________
	1	Excludes a net gain of $49 million from investments in REIT equity securities, a net loss of $3 million from debt of consolidated VIEs, a net gain of$12 million on interest and principal-only securities and other miscellaneous net losses of $2 million recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
			Three Months Ended March 31, 2013
	Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount Long/(Short) March 31, 2013				Amount of
			Long/(Short)							Expiration or							Gain/(Loss)
			31-Dec-12							Exercise							Recognized in
																	Income on
																	Derivatives 1
	Net TBA and forward settling agency securities		$	12,477			43,267			(29,476	)		$	26,268			$	(102	)
	Interest rate swaps		$	(46,850	)		(5,750	)		1,350			$	(51,250	)		54
	Payer swaptions		$	(14,450	)		(11,150	)		2,700			$	(22,900	)		(44		)
	U.S. Treasury securities - short position		$	(11,835	)		(9,935	)		9,210			$	(12,560	)		(3		)
	U.S. Treasury futures contracts - short position		$	—			(800	)		—			$	(800	)		(15		)
																	$	(110	)
	______________________
	1	Excludes a net loss of $1 million on interest and principal-only securities and a net gain of $13 million from debt of consolidated VIEs recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements 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, 2014 and December 31, 2013 (dollars in millions):
			31-Mar-14
	Payer Interest Rate Swaps		Notional				Average			Average			Net				Average
			Amount 1				Fixed			Receive			Estimated				Maturity
							Pay Rate 2			Rate 3			Fair Value				(Years) 4
	≤ 3 years		$	16,650			1.55	%		0.18	%		$	(327	)		1.4
	> 3 to ≤ 5 years		10,575				1.29	%		0.24	%		78				4
	> 5 to ≤ 7 years		6,250				2.09	%		0.25	%		66				5.9
	> 7 to ≤ 10 years		10,175				2.51	%		0.24	%		287				8.5
	> 10 years		2,750				3.17	%		0.24	%		88				14.1
	Total Payer Interest Rate Swaps		$	46,400			1.87	%		0.21	%		$	192			4.9
	________________________
	1	Notional amount includes forward starting swaps of $9.5 billion with an average forward start date of 1.9 years from March 31, 2014.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.57% as of March 31, 2014.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from March 31, 2014 through stated maturity date.
			December 31, 2013
	Payer Interest Rate Swaps 1		Notional				Average		Average		Net				Average
			Amount				Fixed		Receive		Estimated				Maturity
							Pay Rate		Rate		Fair Value				(Years)
	≤ 3 years		$	16,750			1.57%		0.19%		$	(382	)		1.6
	> 3 to ≤ 5 years		10,225				1.07%		0.24%		81				3.9
	> 5 to ≤ 7 years		5,700				1.97%		0.26%		113				6
	> 7 to ≤ 10 years		8,825				2.28%		0.24%		499				8.8
	> 10 years		1,750				2.79%		0.24%		169				14.7
	Total Payer Interest Rate Swaps		$	43,250			1.70%		0.22%		$	480			4.7
	________________________
	1	Notional amount includes forward starting swaps of $4.0 billion with an average forward start date of 1.9 years from December 31, 2013.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.57% as of December 31, 2013.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from December 31, 2013 through stated maturity date.

Pledged_Assets_Tables

Pledged Assets (Tables)	3 Months Ended
	Mar. 31, 2014
Offsetting Liabilities [Line Items]	'
Schedule of Financial Instruments Owned and Pledged as Collateral [Table Text Block]	'
	The following tables summarize our assets pledged as collateral under our 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, 2014 and December 31, 2013 (in millions):
			March 31, 2014
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	52,047	$	1,417	$	56	$	519		$	54,039
	U.S. Treasury securities - fair value		125		—		71		—			196
	Accrued interest on pledged securities		146		4		—		1			151
	Restricted cash		1		—		224		44			269
	Total		$	52,319	$	1,421	$	351	$	564		$	54,655
			December 31, 2013
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	62,708	$	1,459	$	28	$	91		$	64,286
	U.S. Treasury securities - fair value		3,708		—		70		—			3,778
	Accrued interest on pledged securities		189		5		1		—			195
	Restricted cash		3		—		41		57			101
	Total		$	66,608	$	1,464	$	140	$	148		$	68,360
	The cash and cash equivalents and agency securities pledged as collateral under our derivative agreements are included in restricted cash and agency securities, at fair value, respectively, on our consolidated balance sheets.
Schedule of Securities and Cash Pledged as Collateral from Counterparties [Table Text Block]	'
	As of March 31, 2014 and December 31, 2013, we also had assets pledged to us as collateral under our repurchase, reverse repurchase and derivative agreements summarized in the tables below (in millions).
			31-Mar-14
	Assets Pledged to AGNC		Repurchase Agreements		Reverse Repurchase Agreements		Derivative Agreements		Total
	Agency MBS - fair value		$	—	$	—	$	17	$	17
	U.S. Treasury securities - fair value		—		6,658		56		6,714
	Cash		16		—		167		183
	Total		$	16	$	6,658	$	240	$	6,914
			31-Dec-13
	Assets Pledged to AGNC		Repurchase Agreements		Reverse Repurchase Agreements		Derivative Agreements		Total
	Agency MBS - fair value		$	—	$	—	$	82	$	82
	U.S. Treasury securities - fair value		—		1,848		164		2,012
	Cash		—		—		366		366
	Total		$	—	$	1,848	$	612	$	2,460
Offsetting Liabilities [Table Text Block]	'
			Offsetting of Financial Liabilities and Derivative Liabilities
			Gross Amounts of Recognized Liabilities		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Liabilities Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset						Net Amount
									in the
									Consolidated Balance Sheets
									Financial Instruments			Collateral Pledged 2
	31-Mar-14
	Interest rate swap agreements, at fair value 1		$	368	$	—	$	368	$	(288	)	$	(80	)	$	—
	Repurchase agreements		49,729		—		49,729		(4,773		)	(44,806		)	150
	Total derivative, other hedging instruments and other liabilities		$	50,097	$	—	$	50,097	$	(5,061	)	$	(44,886	)	$	150
	31-Dec-13
	Interest rate swap agreements, at fair value 1		$	400	$	—	$	400	$	(331	)	$	(69	)	$	—
	Repurchase agreements		63,533		—		63,533		(1,881		)	(61,652		)	—
	Total derivative, other hedging instruments and other liabilities		$	63,933	$	—	$	63,933	$	(2,212	)	$	(61,721	)	$	—
	_______________________
	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, 2014 and December 31, 2013 (in millions):
			Offsetting of Financial Assets and Derivative Assets
			Gross Amounts of Recognized Assets		Gross Amounts Offset in the Consolidated Balance Sheets		Net Amounts of Assets Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset						Net Amount
									in the
									Consolidated Balance Sheets
									Financial Instruments			Collateral Received 2
	31-Mar-14
	Interest rate swap and swaption agreements, at fair value 1		$	656	$	—	$	656	$	(287	)	$	(240	)	$	129
	Receivable under reverse repurchase agreements		6,685		—		6,685		(4,773		)	(1,912		)	—
	Total derivative, other hedging instruments and other assets		$	7,341	$	—	$	7,341	$	(5,060	)	$	(2,152	)	$	129
	31-Dec-13
	Interest rate swap and swaption agreements, at fair value 1		$	1,138	$	—	$	1,138	$	(331	)	$	(610	)	$	197
	Receivable under reverse repurchase agreements		1,881		—		1,881		(1,881		)	—			—
	Total derivative, other hedging instruments and other assets		$	3,019	$	—	$	3,019	$	(2,212	)	$	(610	)	$	197

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2014
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, 2014 and December 31, 2013 (dollars in millions):
		Fair Value Hierarchy
		Level 1		Level 2		Level 3
	March 31, 2014
	Assets:
	Agency securities	$	—	$	56,377	$	—
	U.S. Treasury securities	196		—		—
	Interest rate swaps	—		560		—
	Payer swaptions	—		96		—
	REIT equity securities	352		—
	U.S. Treasury futures	6		—		—
	TBA securities	—		24		—
	Total	$	554	$	57,057	$	—
	Liabilities:
	Debt of consolidated VIEs	$	—	$	874	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	6,658		—		—
	Interest rate swaps	—		368		—
	TBA securities	—		49		—
	Total	$	6,658	$	1,291	$	—
	December 31, 2013
	Assets:
	Agency securities	$	—	$	65,941	$	—
	U.S. Treasury securities	3,822		—		—
	Interest rate swaps	—		880		—
	Payer swaptions	—		258		—
	REIT equity securities	237		—		—
	U.S. Treasury futures	39		—		—
	TBA securities	—		17		—
	Total	$	4,098	$	67,096	$	—
	Liabilities:
	Debt of consolidated VIEs	$	—	$	910	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	1,848		—		—
	Interest rate swaps	—		400		—
	TBA securities	—		22		—
	Total	$	1,848	$	1,332	$	—

Stockholders_Equity_Equity_Off

Stockholders' Equity Equity Offerings (Tables)	3 Months Ended
	Mar. 31, 2014
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, 2014 and 2013 (in millions):
	Accumulated Other Comprehensive (Loss) Income	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated OCI
								Balance
	Balance as of December 31, 2013	$	(1,087	)	$	(296	)	$	(1,383	)
	OCI before reclassifications	502			—			502
	Amounts reclassified from accumulated OCI	19			43			62
	Balance as of March 31, 2014	$	(566	)	$	(253	)	$	(819	)
	Balance as of December 31, 2012	$	2,040		$	(485	)	$	1,555
	OCI before reclassifications	(863		)	—			(863		)
	Amounts reclassified from accumulated OCI	26			49			75
	Balance as of March 31, 2013	$	1,203		$	(436	)	$	767
	The following table summarizes reclassifications out of accumulated OCI for the three months ended March 31, 2014 and 2013 (in millions):
		Three Months Ended March 31,						Line Item in the Consolidated
								Statements of Comprehensive Income
	Amounts Reclassified from Accumulated OCI	2014			2013			Where Net Income is Presented
	Loss amounts reclassified from accumulated OCI for available-for-sale MBS	$	19		$	26		Gain (loss) on sale of agency securities, net
	Periodic interest costs of interest rate swaps previously designated as hedges under GAAP, net	43			49			Interest expense
	Total reclassifications	$	62		$	75

Organization_Details

Organization (Details)	3 Months Ended
	Mar. 31, 2014
Organization [Abstract]	'
Required distribution of taxable net income on a annual basis	90.00%
Intended Annual Distribution of Taxable Net Income	100.00%

Investment_Securities_Narrativ

Investment Securities (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]	'	'
Gain Loss on Other Debt	($3,000,000)	$13,000,000
Future Prepayment Rate Assumption Of Investment Portfolio	8.00%	7.00%
Fair value of CMO securities and interest-only strips	1,700,000,000	'
Securitized CMO Securities	2,300,000,000	'
CMO and Interest Only, Pricincipal Only Securities, Maximum Loss Exposure	265,000,000	246,000,000
Fair value of agency securities collaterizing debt issued by securitization trust	1,400,000,000	1,500,000,000
Principal balance of agency securities collaterizing debt issued by securitization trust	1,300,000,000	1,400,000,000
Debt Instrument, Face Amount	863,000,000	900,000,000
Other Long-term Debt	874,000,000	910,000,000
Agency Securities [Member]	'	'
Schedule of Available-for-sale Securities [Line Items]	'	'
Debt Instrument, Unamortized Discount (Premium), Net	$2,600,000,000	$3,000,000,000

Investment_Securities_Summary_

Investment Securities (Summary of Investment in Agency Security) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Available-for-sale Securities Pledged as Collateral	$51,850,000,000		$62,205,000,000
Amortized cost	56,513,000,000		66,593,000,000
Total agency MBS, at fair value	56,377,000,000		65,941,000,000
Weighted average coupon	3.65%		3.58%	[1]
Weighted average yield	2.72%		2.70%	[2]
Weighted average yield for the year ended	2.54%	[2]	2.77%	[2]
Unamortized principal balance of interest-only strips	1,300,000,000		1,400,000,000
Unamortized principal balance of principal-only strips	265,000,000		271,000,000
Weighted average contractual interest rate of interest only strips	5.49%		5.50%
Average prepayment rate based on forward rate assumption	8.00%		7.00%
Restricted Cash and Cash Equivalents	269,000,000		101,000,000
Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]	'		'
Total agency MBS, at fair value	43,993,000,000		52,693,000,000
Weighted average coupon	3.62%	[1]	3.53%	[1]
Weighted average yield	2.70%	[2]	2.66%	[2]
Weighted average yield for the year ended	2.53%	[2]	2.74%	[2]
Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]	'		'
Total agency MBS, at fair value	12,165,000,000		13,013,000,000
Weighted average coupon	3.75%	[1]	3.78%	[1]
Weighted average yield	2.82%	[2]	2.87%	[2]
Weighted average yield for the year ended	2.61%	[2]	2.87%	[2]
Government National Mortgage Association Certificates and Obligations (GNMA) [Member]	'		'
Total agency MBS, at fair value	219,000,000		235,000,000
Weighted average coupon	3.54%	[1]	3.56%	[1]
Weighted average yield	1.66%	[2]	1.66%	[2]
Weighted average yield for the year ended	1.67%	[2]	1.79%	[2]
Available-for-sale Securities [Member]	'		'
Agency MBS, par	54,070,000,000		63,777,000,000
Unamortized discount	23,000,000		32,000,000
Unamortized premium	2,466,000,000		2,848,000,000
Amortized cost	56,513,000,000		66,593,000,000
Gross unrealized gains	335,000,000		260,000,000
Gross unrealized losses	903,000,000		1,349,000,000
Total available-for-sale agency MBS, at fair value	55,945,000,000		65,504,000,000
Available-for-sale Securities [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]	'		'
Agency MBS, par	42,131,000,000		50,914,000,000
Unamortized discount	17,000,000		25,000,000
Unamortized premium	1,887,000,000		2,210,000,000
Amortized cost	44,001,000,000		53,099,000,000
Gross unrealized gains	238,000,000		181,000,000
Gross unrealized losses	646,000,000		991,000,000
Total available-for-sale agency MBS, at fair value	43,593,000,000		52,289,000,000
Available-for-sale Securities [Member] | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]	'		'
Agency MBS, par	11,730,000,000		12,640,000,000
Unamortized discount	6,000,000		7,000,000
Unamortized premium	573,000,000		631,000,000
Amortized cost	12,297,000,000		13,264,000,000
Gross unrealized gains	93,000,000		74,000,000
Gross unrealized losses	257,000,000		358,000,000
Total available-for-sale agency MBS, at fair value	12,133,000,000		12,980,000,000
Available-for-sale Securities [Member] | Government National Mortgage Association Certificates and Obligations (GNMA) [Member]	'		'
Agency MBS, par	209,000,000		223,000,000
Unamortized discount	0		0
Unamortized premium	6,000,000		7,000,000
Amortized cost	215,000,000		230,000,000
Gross unrealized gains	4,000,000		5,000,000
Gross unrealized losses	0		0
Total available-for-sale agency MBS, at fair value	219,000,000		235,000,000
Agency MBS remeasured at fair value through earnings [Member]	'		'
Interest-only and principal-only strips, amortized cost	415,000,000		432,000,000
Gross unrealized gains	24,000,000		16,000,000
Gross unrealized losses	-7,000,000		-11,000,000
Total agency MBS remeasured at fair value through earnings, at fair value	432,000,000		437,000,000
Agency MBS remeasured at fair value through earnings [Member] | Federal National Mortgage Association Certificates and Obligations (FNMA) [Member]	'		'
Interest-only and principal-only strips, amortized cost	386,000,000		400,000,000
Gross unrealized gains	20,000,000		13,000,000
Gross unrealized losses	-6,000,000		-9,000,000
Total agency MBS remeasured at fair value through earnings, at fair value	400,000,000		404,000,000
Agency MBS remeasured at fair value through earnings [Member] | Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member]	'		'
Interest-only and principal-only strips, amortized cost	29,000,000		32,000,000
Gross unrealized gains	4,000,000		3,000,000
Gross unrealized losses	-1,000,000		-2,000,000
Total agency MBS remeasured at fair value through earnings, at fair value	32,000,000		33,000,000
Agency MBS remeasured at fair value through earnings [Member] | Government National Mortgage Association Certificates and Obligations (GNMA) [Member]	'		'
Interest-only and principal-only strips, amortized cost	0		0
Gross unrealized gains	0		0
Gross unrealized losses	0		0
Total agency MBS remeasured at fair value through earnings, at fair value	0		0
Assets Pledged to Us [Member]	'		'
Available-for-sale Securities Pledged as Collateral	17,000,000		82,000,000
Restricted Cash and Cash Equivalents	183,000,000		366,000,000
Assets Pledged to Us [Member] | Derivative [Member]	'		'
Available-for-sale Securities Pledged as Collateral	17,000,000		82,000,000
Derivative [Member]	'		'
Available-for-sale Securities Pledged as Collateral	56,000,000		28,000,000
Restricted Cash and Cash Equivalents	224,000,000		41,000,000
Derivative [Member] | Assets Pledged to Us [Member]	'		'
Restricted Cash and Cash Equivalents	$167,000,000		$366,000,000
[1]	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.3 billion and the weighted average contractual interest we are entitled to receive was 5.49% of this amount as of MarchB 31, 2014. The par value of our principal-only agency MBS strips was $265 million as of MarchB 31, 2014.
[2]	Incorporates a weighted average future constant prepayment rate assumption of 8% based on forward rates as of MarchB 31, 2014

Investment_Securities_Componen

Investment Securities (Components Of Investment Securities) (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Amortized cost	$56,928	$67,025
Gross unrealized gains	359	276
Gross unrealized losses	-910	-1,360
Available-for-sale Securities, Fair Value Disclosure	55,945	65,504
Available-for-sale Securities, Amortized Cost Basis	56,513	66,593
Total agency MBS, at fair value	56,377	65,941
Total Agency Securities	56,377	65,941
Fixed-Rate [Member]	'	'
Gross unrealized gains	307	242
Gross unrealized losses	-902	-1,338
Available-for-sale Securities, Fair Value Disclosure	53,461	62,961
Adjustable-Rate [Member]	'	'
Gross unrealized gains	19	15
Gross unrealized losses	0	-3
Available-for-sale Securities, Fair Value Disclosure	1,195	1,235
CMO [Member]	'	'
Gross unrealized gains	9	3
Gross unrealized losses	-1	-8
Available-for-sale Securities, Fair Value Disclosure	1,289	1,308
Agency Securities [Member] | Fixed-Rate [Member]	'	'
Available-for-sale Securities, Amortized Cost Basis	54,056	64,057
Agency Securities [Member] | Adjustable-Rate [Member]	'	'
Available-for-sale Securities, Amortized Cost Basis	1,176	1,223
Agency Securities [Member] | CMO [Member]	'	'
Available-for-sale Securities, Amortized Cost Basis	1,281	1,313
Agency Securities [Member] | Interest Only And Principal Only Strip [Member]	'	'
Amortized cost	415	432
Gross unrealized gains	24	16
Gross unrealized losses	-7	-11
Fair Value	$432	$437

Investment_Securities_Summary_1

Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Weighted Average Life Interest Only Securities	'6 years 2 months	'6 years 4 months
Weighted Average Life Principal Only Securities	'8 years 4 months	'8 years 7 months
Agency securities classified as available for sale, Fair value	$55,945	$65,504
Agency securities classified as available for sale, Amortized cost	56,513	66,593
Weighted average coupon	3.53%	3.47%
Available For Sale Securities Weighted Average Life yield	2.70%	2.68%
Less Than or Equal to One Year [Member]	'	'
Available For Sale Securities Weighted Average Life Fair Value	27	129
Available For Sale Securities Weighted Average Life Amortized Cost	25	129
Weighted average coupon	2.49%	3.07%
Available For Sale Securities Weighted Average Life yield	1.81%	2.53%
Greater Than One Year and Less Than or Equal to Three Years [Member]	'	'
Available For Sale Securities Weighted Average Life Fair Value	191	498
Available For Sale Securities Weighted Average Life Amortized Cost	186	491
Weighted average coupon	4.86%	4.08%
Available For Sale Securities Weighted Average Life yield	3.29%	2.25%
Greater Than Three Years and Less Than or Equal to Five Years [Member]	'	'
Available For Sale Securities Weighted Average Life Fair Value	22,947	24,471
Available For Sale Securities Weighted Average Life Amortized Cost	22,758	24,342
Weighted average coupon	3.55%	3.59%
Available For Sale Securities Weighted Average Life yield	2.53%	2.57%
Greater Than Five Years [Member]	'	'
Available For Sale Securities Weighted Average Life Fair Value	32,534	38,522
Available For Sale Securities Weighted Average Life Amortized Cost	33,284	39,635
Weighted average coupon	3.51%	3.39%
Available For Sale Securities Weighted Average Life yield	2.80%	2.73%
Greater Than Ten Years [Member]	'	'
Available For Sale Securities Weighted Average Life Fair Value	246	1,884
Available For Sale Securities Weighted Average Life Amortized Cost	$260	$1,996
Weighted average coupon	3.61%	3.66%
Available For Sale Securities Weighted Average Life yield	2.87%	2.96%

Investment_Securities_Summary_2

Investment Securities (Summary Of Changes In Accumulated OCI For Available-For-Sale Security) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'	'
Unrealized gain (loss) on available-for-sale securities, net	$521	($837)
Agency Securities [Member]	'	'
Accumulated Other Comprehensive Income (Loss) [Roll Forward]	'	'
Beginning OCI Balance	-1,087	2,040
Unrealized gain (loss) on available-for-sale securities, net	502	-863
Reversal of prior Period Unrealized (Gains) and Losses, Net on Realization	19	26
Ending OCI Balance	($566)	$1,203

Investment_Securities_Summary_3

Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) (Accumulated Other Comprehensive Income (Loss) [Member], USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Member]	'	'	'
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$22,112	$25,963	$42,853
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	-442	-174	-1,248
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	8,673	84	1,586
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	-461	-2	-101
Unrealized Loss Position For - Estimated Fair Value - Total	30,785	26,047	44,439
Unrealized Loss Position For - Unrealized Loss - Total	($903)	($176)	($1,349)

Investment_Securities_Summary_4

Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Proceeds from agency MBS sold	($12,807)	($10,001)
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	-19	-26
Agency Securities [Member]	'	'
Agency MBS sold, at cost	-9,711	-20,328
Proceeds from agency MBS sold	-9,692	-20,302
Gain (Loss) on Sales of Mortgage Backed Securities (MBS)	-19	-26
Gross gains on sale of agency MBS	42	87
Gross losses on sale of agency MBS	61	113
Interest Only And Principal Only Strip [Member]	'	'
Unrealized Gain (Loss) on Securities	$12	($1)

Repurchase_Agreements_And_Othe1

Repurchase Agreements And Other Debt (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]	'	'
Weighted Average Life of Other Debt	'6 years 6 months	'
Other Long-term Debt	$874	$910
Debt Instrument, Face Amount	$863	$900
Debt Instrument, Description of Variable Rate Basis, LIBOR	'	'LIBOR
Spread Over LIBOR	'43	'42

Repurchase_Agreements_And_Othe2

Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Other Long-term Debt	$874	$910
Spread Over LIBOR	'43	'42
Debt Instrument, Face Amount	863	900
Borrowings Outstanding	49,729	63,533
Weighted Average Days to Maturity	161	119
30 Days or Less [Member]	'	'
Borrowings Outstanding	13,440	23,577
Average Interest Rate	0.37%	0.42%
Weighted Average Days to Maturity	15	15
thirty one to ninety [Member]	'	'
Borrowings Outstanding	17,396	20,490
Average Interest Rate	0.38%	0.43%
Weighted Average Days to Maturity	54	61
120 to 180 days [Member]	'	'
Borrowings Outstanding	5,242	6,946
Average Interest Rate	0.45%	0.45%
Weighted Average Days to Maturity	137	140
210 to 270 days [Member]	'	'
Borrowings Outstanding	4,560	2,232
Average Interest Rate	0.51%	0.53%
Weighted Average Days to Maturity	232	230
300 to 360 days [Member]	'	'
Borrowings Outstanding	4,171	3,607
Average Interest Rate	0.49%	0.54%
Weighted Average Days to Maturity	326	323
390 to 720 days [Member]	'	'
Borrowings Outstanding	3,232	3,261
Average Interest Rate	0.57%	0.60%
Weighted Average Days to Maturity	517	603
750 to 1080 days [Member]	'	'
Borrowings Outstanding	540	500
Average Interest Rate	0.61%	0.62%
Weighted Average Days to Maturity	876	930
Greater than 1080 days [Member]	'	'
Borrowings Outstanding	999	602
Average Interest Rate	0.66%	0.68%
Weighted Average Days to Maturity	1,599	1,468
US Treasury Securities [Member]	'	'
Borrowings Outstanding	149	2,318
Average Interest Rate	0.05%	0.02%
Weighted Average Days to Maturity	1	1
Repurchase Agreements [Member]	'	'
Average Interest Rate	0.43%	0.44%
Agency Securities [Member]	'	'
Borrowings Outstanding	$49,580	$61,215
Weighted Average Days to Maturity	162	124
Agency Securities [Member] | Repurchase Agreements [Member]	'	'
Average Interest Rate	0.43%	0.45%

Derivative_and_Other_Hedging_I2

Derivative and Other Hedging Instruments (Narrative) (Details) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

Interest Rate Swaps [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Inputs, Level 2 [Member]

Fair Value, Measurements, Recurring [Member]

Fair Value, Measurements, Recurring [Member]

Purchases Of TBAs And Forward Settling Agency Securities [Member]

Derivative assets, at fair value

$686,000,000

'

$1,194,000,000

'

'

'

'

'

'

'

$17,000,000

$24,000,000

Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion

83,000,000

84,000,000

'

'

'

'

'

'

'

'

'

'

Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax

43,000,000

49,000,000

'

'

'

43,000,000

49,000,000

'

'

'

'

'

Net Periodic Interest Rate Costs on Swaps

126,000,000

133,000,000

'

'

'

'

'

'

'

'

'

'

Gain On Interest Only Securities Remeasured at Fair Value Through Earnings

'

-1,000,000

'

'

'

'

'

'

'

'

'

'

Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge

'

'

'

'

'

-253,000,000

-436,000,000

296,000,000

485,000,000

'

'

'

Derivative, Average Remaining Maturity

'

'

'

'4 years 10 months 15 days

'4 years 8 months

'

'

'

'

'1 year 11 months

'

'

Obligation to return securities borrowed under reverse repurchase agreements, at fair value

6,658,000,000

'

1,848,000,000

'

'

'

'

'

'

'

'

'

Proceeds from sales of treasury securities

6,700,000,000

'

1,900,000,000

'

'

'

'

'

'

'

'

'

Deferred gain loss discontinued interest rate swap expected to be reclassified from OCI to interest expense next twelve months

'

'

'

'

'

143,000,000

'

'

'

'

'

'

Interest rate swap agreement outstanding not designated as hedge

8,000,000,000

'

'

46,400,000,000

43,250,000,000

'

'

'

'

'

'

'

Credit Derivative, Maximum Exposure, Undiscounted

0.01

'

'

'

'

'

'

'

'

'

'

'

Variable Interest Entity, Measure of Activity, Expense

($3,000,000)

$13,000,000

'

'

'

'

'

'

'

'

'

'

Derivative_and_Other_Hedging_I3

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps) (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Options At Cost	$194	'	'
Derivative, Higher Remaining Maturity Range	'1 year 10 months 15 days	'	'1 year 10 months 14 days
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	83	84	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	43	49	'
Interest Rate Derivatives, at Fair Value, Net	93	'	'
Notional Amount	8,000	'	'
Interest Rate Swap [Member]	'	'	'
Derivative, Average Fixed Interest Rate	1.87%	'	1.70%
Notional Amount	46,400	'	43,250
Derivative, Average Remaining Maturity	'4 years 10 months 15 days	'	'4 years 8 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	43	49	'
Interest Rate Swap [Member]	'	'	'
Derivative, Notional Amount	9,500	'	'
Interest Rate Swaps Excluding Forward Starting [Member] | Interest Rate Swap [Member]	'	'	'
Derivative, Average Fixed Interest Rate	1.57%	'	1.57%
Less Than or Equal to One Year [Member] | Receiver Interest Rate Swaps [Member]	'	'	'
Options At Cost	3	'	'
Derivative, Average Fixed Interest Rate	2.26%	'	'
Interest Rate Derivatives, at Fair Value, Net	3	'	'
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	12	'	'
Notional Amount	$1,000	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'3M	'	'
Derivative, Average Remaining Maturity	'10 years	'	'

Derivative_and_Other_Hedging_I4

Derivative and Other Hedging Instruments (Remaining Interest Rate Swap Term) (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Unrealized (loss) gain on derivative instruments, net	$43	$49	'
Notional Amount	8,000	'	'
Remaining interest rate swap term, maximum	'1 year 10 months 15 days	'	'1 year 10 months 14 days
Interest Rate Swap [Member]	'	'	'
Notional Amount	46,400	'	43,250
Derivative, Average Remaining Maturity	'4 years 10 months 15 days	'	'4 years 8 months
Average Fixed Pay Rate	1.87%	'	1.70%
Average Receive Rate	0.21%	'	0.22%
Net Estimated Fair Value	192	'	480
Interest Rate Swap [Member]	'	'	'
Derivative, Notional Amount	$9,500	'	'

Derivative_and_Other_Hedging_I5

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps Designated As Hedging Instruments) (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Derivative [Line Items]	'	'	'
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$83	$84	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	43	49	'
Derivative, Higher Remaining Maturity Range	'1 year 10 months 15 days	'	'1 year 10 months 14 days
Notional Amount	8,000	'	'
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]	'	'	'
Derivative [Line Items]	'	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	43	49	'
Interest Rate Swap [Member]	'	'	'
Derivative [Line Items]	'	'	'
Derivative, Average Remaining Maturity	'4 years 10 months 15 days	'	'4 years 8 months
Derivative, Average Fixed Interest Rate	1.87%	'	1.70%
Notional Amount	46,400	'	43,250
Interest Rate Swap [Member] | Forward Contracts [Member]	'	'	'
Derivative [Line Items]	'	'	'
Derivative, Notional Amount	'	'	4,000
Interest Rate Swap [Member] | Interest Rate Swaps Excluding Forward Starting [Member]	'	'	'
Derivative [Line Items]	'	'	'
Derivative, Average Fixed Interest Rate	1.57%	'	1.57%
Interest Rate Swaps [Member] | Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]	'	'	'
Derivative [Line Items]	'	'	'
Derivative, Average Remaining Maturity	'1 year 11 months	'	'

Derivative_and_Other_Hedging_I6

Derivative and Other Hedging Instruments (Effect Of Interest Rate Swaps Designated As Hedges) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Derivatives, Fair Value [Line Items]	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$43	$49
Net Periodic Interest Rate Costs on Swaps	126	133
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	83	84
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]	'	'
Derivatives, Fair Value [Line Items]	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$43	$49

Derivative_and_Other_Hedging_I7

Derivative and Other Hedging Instruments (Summary Of Outstanding Forward Contracts Designated As Hedging Instruments) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
			Interest Rate Swap [Member]	Interest Rate Swap [Member]
Net Periodic Interest Rate Costs on Swaps	$126	$133	'	'
Notional Amount	8,000	'	46,400	43,250
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	$83	$84	'	'

Derivative_and_Other_Hedging_I8

Derivative and Other Hedging Instruments (Effect of Forward Contracts Designated as Hedges) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Notional Amount	$8,000	'
Unrealized (loss) gain on derivative instruments, net	$43	$49

Derivative_and_Other_Hedging_I9

Derivative and Other Hedging Instruments (Summary of Long and Short Position of Derivative Instruments) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Gain (loss) on REIT Equity Securities	$49		'	'
Variable Interest Entity, Measure of Activity, Expense	-3		13	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-434		-110	'
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	686		'	1,194
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	-417		'	-422
Interest Rate Swap [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-380		54	'
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	-368		'	-400
Interest Rate Swaption [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	-105		-44	'
Purchases Of TBAs And Forward Settling Agency Securities [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	'		'	17
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	-49		'	-22
TBA securities Fifteen Year and Thirty Year Securities [Member]	'		'	'
Derivative, Forward Settlement Value	14,127		'	2,276
Derivative Asset, Fair Value, Gross Asset	14,102		'	2,271
Fair Value of Derivative Instruments	-25	[1]	'	-5	[1]
TBA securities Fifteen Year and Thirty Year Securities [Member] | Long [Member]	'		'	'
Derivative, Forward Settlement Value	18,136		'	6,882
Derivative Asset, Fair Value, Gross Asset	18,095		'	6,864
Fair Value of Derivative Instruments	-41		'	-18
TBA securities Fifteen Year and Thirty Year Securities [Member] | Short [Member]	'		'	'
Derivative, Forward Settlement Value	-4,009		'	-4,606
Derivative Liability, Fair Value, Gross Liability	-3,993		'	-4,593
Fair Value of Derivative Instruments	16		'	13
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swap [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	560		'	880
Fair Value, Inputs, Level 2 [Member] | Interest Rate Swaption [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	96		'	258
Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member] | Future [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	6		'	-39
Interest Only And Principal Only Strip [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	12		'	'
Other Derivatives [Member]	'		'	'
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	($2)		'	'
[1]	1.Notional amount represents the par value (or principal balance) of the underlying agency security.

Recovered_Sheet2

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps Agreements Not Designated As Hedges) (Details) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

Put Option [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than Three Years and Less Than or Equal to Five Years [Member]

Greater Than Three Years and Less Than or Equal to Five Years [Member]

Greater Than Five Years and Less than or Equal to Seven Years [Member]

Greater Than Five Years and Less than or Equal to Seven Years [Member]

Greater Than Seven Years and Less than or Equal to Ten Years [Member]

Greater Than Seven Years and Less than or Equal to Ten Years [Member]

Greater Than Ten Years [Member]

Greater Than Ten Years [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Short [Member]

Short [Member]

Short [Member]

Short [Member]

Long [Member]

Long [Member]

Future [Member]

Future [Member]

Future [Member]

Future [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Receiver Swaption [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value

$6,658,000,000

'

$1,848,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value

686,000,000

'

1,194,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notional Amount

8,000,000,000

'

'

46,400,000,000

'

43,250,000,000

'

'

14,250,000,000

13,909,000,000

26,268,000,000

2,119,000,000

12,477,000,000

'

16,650,000,000

16,750,000,000

2,450,000,000

3,600,000,000

10,575,000,000

10,225,000,000

6,250,000,000

5,700,000,000

10,175,000,000

8,825,000,000

2,750,000,000

1,750,000,000

-46,400,000,000

-43,250,000,000

-51,250,000,000

-46,850,000,000

-14,250,000,000

-22,900,000,000

-14,450,000,000

1,000,000,000

-6,786,000,000

-12,560,000,000

-2,007,000,000

-11,835,000,000

'

'

-730,000,000

-800,000,000

-1,730,000,000

0

Net Estimated Fair Value

'

'

'

192,000,000

'

480,000,000

'

'

'

'

'

'

'

'

-327,000,000

-382,000,000

'

'

78,000,000

81,000,000

66,000,000

113,000,000

287,000,000

499,000,000

88,000,000

169,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value

417,000,000

'

422,000,000

368,000,000

'

400,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period

'

'

'

-5,900,000,000

-5,750,000,000

'

'

-11,150,000,000

'

24,376,000,000

43,267,000,000

'

'

-50,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-7,241,000,000

-9,935,000,000

'

'

'

'

-730,000,000

-800,000,000

'

'

Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period

'

'

'

2,750,000,000

1,350,000,000

'

7,250,000,000

2,700,000,000

'

'

-29,476,000,000

'

'

50,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,462,000,000

9,210,000,000

'

'

'

'

1,730,000,000

0

'

'

Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net

-434,000,000

-110,000,000

'

-380,000,000

54,000,000

'

-105,000,000

-44,000,000

'

60,000,000

-102,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-45,000,000

-3,000,000

'

'

72,000,000

'

-36,000,000

-15,000,000

'

'

Trading Securities Added During the Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,900,000,000

'

'

'

'

'

Notional Amount Of Trading Securities Settlement Expiration During The Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-5,627,000,000

'

'

'

'

'

Trading Securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000,000

3,927,000,000

'

'

'

'

Term (Years)

'

'

'

'4 years 10 months 15 days

'

'4 years 8 months

'5 years 8 months

'

'7 years

'

'

'

'

'

'1 year 4 months 15 days

'1 year 7 months

'4 years 6 months

'5 years 7 months

'4 years

'3 years 11 months

'5 years 10 months 15 days

'6 years

'8 years 6 months

'8 years 9 months

'14 years 1 month

'14 years 8 months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Proceeds from Securities Purchased under Agreements to Resell

$6,700,000,000

'

$1,900,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Average Fixed Interest Rate

'

'

'

1.87%

'

1.70%

3.27%

'

3.09%

'

'

'

'

'

1.55%

1.57%

3.55%

3.40%

1.29%

1.07%

2.09%

1.97%

2.51%

2.28%

3.17%

2.79%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Average Variable Interest Rate

'

'

'

0.21%

'

0.22%

'

'

'

'

'

'

'

'

0.18%

0.19%

'

'

0.24%

0.24%

0.25%

0.26%

0.24%

0.24%

0.24%

0.24%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recovered_Sheet3

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps Agreements Designated As Hedges in the Future) (Details) (USD $)	3 Months Ended	12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Cost	194	'
Fair Value	93	'
Notional Amount	8,000	'
Payer Swaption [Member]	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'3M	'3M
Interest Rate Swaption [Member]	'	'
Cost	'	335
Fair Value	'	258
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	12	10
Notional Amount	'	14,250
Average Fixed Pay Rate	3.27%	3.09%
Term (Years)	'5 years 8 months	'7 years
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member] | Interest Rate Swaps [Member]	'	'
Term (Years)	'1 year 11 months	'
Less Than or Equal to One Year [Member] | Payer Swaption [Member]	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'3M	'3M
Less Than or Equal to One Year [Member] | Interest Rate Swaption [Member]	'	'
Cost	111	193
Fair Value	44	117
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	5	4
Notional Amount	4,650	9,400
Average Fixed Pay Rate	2.98%	2.87%
Term (Years)	'6 years 5 months	'7 years 9 months
Greater Than One Year and Less Than or Equal to Three Years [Member] | Payer Swaption [Member]	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'3M	'3M
Greater Than One Year and Less Than or Equal to Three Years [Member] | Interest Rate Swaption [Member]	'	'
Cost	60	105
Fair Value	34	92
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	18	19
Notional Amount	2,450	3,600
Average Fixed Pay Rate	3.55%	3.40%
Term (Years)	'4 years 6 months	'5 years 7 months
greater than two years less than or equal to three years [Member] | Payer Swaption [Member]	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'3M	'3M
greater than two years less than or equal to three years [Member] | Interest Rate Swaption [Member]	'	'
Cost	23	35
Fair Value	15	45
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	28	30
Notional Amount	900	1,150
Average Fixed Pay Rate	3.99%	3.81%
Term (Years)	'5 years 5 months	'5 years 9 months
greater than four years less than or equal to five years [Member] | Payer Swaption [Member]	'	'
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	'	'3M
greater than four years less than or equal to five years [Member] | Interest Rate Swaption [Member]	'	'
Cost	'	2
Fair Value	'	4
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration	'	52
Notional Amount	'	100
Average Fixed Pay Rate	'	4.80%
Term (Years)	'	'7 years

Recovered_Sheet4

Derivative and Other Hedging Instruments (Summary of Outstanding TBAs) (Details) (TBA securities Fifteen Year and Thirty Year Securities [Member], USD $)	Mar. 31, 2014		Dec. 31, 2013
In Millions, unless otherwise specified
Derivative [Line Items]	'		'
Derivative Asset, Fair Value, Gross Asset	$14,102		$2,271
Notional Amount	13,909	[1]	2,119	[1]
Derivative, Forward Settlement Value	14,127		2,276
Fair Value of Derivative Instruments	-25	[1]	-5	[1]
Long [Member]	'		'
Derivative [Line Items]	'		'
Derivative Asset, Fair Value, Gross Asset	18,095		6,864
Notional Amount	17,699		6,660
Derivative, Forward Settlement Value	18,136		6,882
Fair Value of Derivative Instruments	-41		-18
Short [Member]	'		'
Derivative [Line Items]	'		'
Derivative Liability, Fair Value, Gross Liability	-3,993		-4,593
Notional Amount	-3,790		-4,541
Derivative, Forward Settlement Value	-4,009		-4,606
Fair Value of Derivative Instruments	$16		$13
[1]	1.Notional amount represents the par value (or principal balance) of the underlying agency security.

Recovered_Sheet5

Derivative and Other Hedging Instruments (Summary Of Derivatives Outstanding Not Designated As Hedging Instruments) (Details) (USD $)

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

12 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

3 Months Ended

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Mar. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Dec. 31, 2013

Mar. 31, 2014

Mar. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Mar. 31, 2014

Put Option [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

TBA and Forward Settling Agency Securities [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Payer Swaption [Member]

Purchases Of TBAs And Forward Settling Agency Securities [Member]

Purchases Of TBAs And Forward Settling Agency Securities [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]

Less Than or Equal to One Year [Member]

Less Than or Equal to One Year [Member]

Less Than or Equal to One Year [Member]

Less Than or Equal to One Year [Member]

Less Than or Equal to One Year [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

Greater Than One Year and Less Than or Equal to Three Years [Member]

greater than two years less than or equal to three years [Member]

greater than two years less than or equal to three years [Member]

greater than two years less than or equal to three years [Member]

greater than two years less than or equal to three years [Member]

greater than four years less than or equal to five years [Member]

greater than four years less than or equal to five years [Member]

Receiver Swaption [Member]

Payer Swaption [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Not Designated as Hedging Instrument [Member]

Short [Member]

Short [Member]

Short [Member]

Short [Member]

Long [Member]

Long [Member]

Future [Member]

Future [Member]

Future [Member]

Future [Member]

Other derivative instruments [Member]

years

years

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Payer Swaption [Member]

Receiver Swaption [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Payer Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Payer Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swap [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Interest Rate Swaption [Member]

Payer Swaption [Member]

Receiver Swaption [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

US Treasury Securities [Member]

years

years

years

years

years

years

years

years

Options At Cost

$194,000,000

'

'

'

'

'

'

'

'

'

'

'

'

$335,000,000

'

'

'

'

'

'

'

'

$111,000,000

$193,000,000

'

'

$3,000,000

'

'

$60,000,000

$105,000,000

'

'

$23,000,000

$35,000,000

'

'

$2,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Rate Derivatives, at Fair Value, Net

93,000,000

'

'

'

'

'

'

'

'

'

'

'

'

258,000,000

'

'

'

'

'

'

'

'

44,000,000

117,000,000

'

'

3,000,000

'

'

34,000,000

92,000,000

'

'

15,000,000

45,000,000

'

'

4,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration

'

'

'

'

'

'

'

'

'

'

'

12

'

10

'

'

'

'

'

'

'

'

5

4

'

'

12

'

'

18

19

'

'

28

30

'

'

52

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notional Amount

8,000,000,000

'

'

'

13,909,000,000

26,268,000,000

2,119,000,000

12,477,000,000

46,400,000,000

'

43,250,000,000

'

'

14,250,000,000

'

'

'

'

'

'

'

'

4,650,000,000

9,400,000,000

'

'

1,000,000,000

16,650,000,000

16,750,000,000

2,450,000,000

3,600,000,000

'

'

900,000,000

1,150,000,000

'

'

100,000,000

'

'

'

-46,400,000,000

-43,250,000,000

-51,250,000,000

-46,850,000,000

-14,250,000,000

-22,900,000,000

-14,450,000,000

-8,000,000,000

1,000,000,000

-6,786,000,000

-12,560,000,000

-2,007,000,000

-11,835,000,000

'

'

-730,000,000

-800,000,000

-1,730,000,000

0

'

Derivative, Average Fixed Interest Rate

'

'

'

'

'

'

'

'

1.87%

'

1.70%

3.27%

'

3.09%

'

'

'

'

'

'

'

'

2.98%

2.87%

'

'

2.26%

1.55%

1.57%

3.55%

3.40%

'

'

3.99%

3.81%

'

'

4.80%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'3M

'3M

'

'

'

'

'

'

'

'

'3M

'3M

'3M

'

'

'

'

'3M

'3M

'

'

'3M

'3M

'

'3M

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Gain On Interest Only Securities Remeasured at Fair Value Through Earnings

'

-1,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net

-434,000,000

-110,000,000

'

'

60,000,000

-102,000,000

'

'

-380,000,000

54,000,000

'

-105,000,000

-44,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-45,000,000

-3,000,000

'

'

72,000,000

'

-36,000,000

-15,000,000

'

'

-2,000,000

Trading Securities

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

200,000,000

3,927,000,000

'

'

'

'

'

Trading Securities Added During the Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,900,000,000

'

'

'

'

'

'

Notional Amount Of Trading Securities Settlement Expiration During The Period

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

-5,627,000,000

'

'

'

'

'

'

Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period

'

'

'

50,000,000

'

-29,476,000,000

'

'

2,750,000,000

1,350,000,000

'

7,250,000,000

2,700,000,000

'

'

'

-12,586,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2,462,000,000

9,210,000,000

'

'

'

'

1,730,000,000

0

'

'

'

Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax

43,000,000

49,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

43,000,000

49,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative assets not designated as hedging instruments

686,000,000

'

1,194,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

17,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative liabilities not designated as hedging instruments

417,000,000

'

422,000,000

'

'

'

'

'

368,000,000

'

400,000,000

'

'

'

'

'

49,000,000

22,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

253,000,000

436,000,000

-296,000,000

-485,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Term (Years)

'

'

'

'

'

'

'

'

'4 years 10 months 15 days

'

'4 years 8 months

'5 years 8 months

'

'7 years

'

'

'

'

'

'

'

'

'6 years 5 months

'7 years 9 months

'

'

'10 years

'1 year 4 months 15 days

'1 year 7 months

'4 years 6 months

'5 years 7 months

'

'

'5 years 5 months

'5 years 9 months

'

'

'7 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Deferred gain loss discontinued interest rate swap expected to be reclassified from OCI to interest expense next twelve months

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

143,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Derivative, Higher Remaining Maturity Range

'1 year 10 months 15 days

'

'1 year 10 months 14 days

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period

'

'

'

-50,000,000

24,376,000,000

43,267,000,000

'

'

-5,900,000,000

-5,750,000,000

'

'

-11,150,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000,000

-1,000,000,000

'

'

'

'

'

'

'

'

'

-7,241,000,000

-9,935,000,000

'

'

'

'

-730,000,000

-800,000,000

'

'

'

Credit Derivative, Maximum Exposure, Undiscounted

$0.01

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Recovered_Sheet6

Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Income Statement) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Notional Amount	'	'	$8,000
Amount Gain/(Loss) Recognized in Income on Derivatives	-434	-110	'
Interest Only And Principal Only Strip [Member]	'	'	'
Unrealized Gain (Loss) on Securities	$12	($1)	'

Pledged_Assets_Details

Pledged Assets (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Offsetting Assets and Liabilities [Line Items]	'	'
Risk Of Repurchase Agreement To Stockholders Equity	4.00%	'
Security Owned and Pledged as Collateral, Fair Value	$53,589,000,000	$67,875,000,000
Available-for-sale Securities Pledged as Collateral	51,850,000,000	62,205,000,000
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	6,658,000,000	1,848,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-2,152,000,000	'
Derivative Liability, Fair Value, Amount Offset Against Collateral	150,000,000	'
Available For Sale Securities Pledged As Collateral Accrued Interest	151,000,000	195,000,000
Restricted Cash and Cash Equivalents	269,000,000	101,000,000
Total Fair Value Of Agency Securities Pledged And Accrued Interest	54,655,000,000	68,360,000,000
Agency Securities Pledged As Collateral Amortized Cost	54,156,000,000	69,008,000,000
Agency Securities Pledged As Collateral Accrued Interest	'	194,000,000
Credit Derivative, Maximum Exposure, Undiscounted	0.01	'
Liability [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	50,097,000,000	63,933,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	50,097,000,000	63,933,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-5,061,000,000	-2,212,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-44,886,000,000	-61,721,000,000
Liability [Member] | Swaption [Member] | Interest Rate Swap [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	368,000,000	400,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	368,000,000	400,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-288,000,000	-331,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-80,000,000	-69,000,000
Assets [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	7,341,000,000	3,019,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	7,341,000,000	3,019,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-5,060,000,000	-2,212,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	'	-610,000,000
Net Amount After Deducting Gross Amounts Not Offset on the Balance Sheet From Net Amount of Assets (Liabilities) Presented on the Balance Sheet	129,000,000	197,000,000
Assets [Member] | Swaption [Member] | Interest Rate Swap [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	656,000,000	1,138,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	656,000,000	1,138,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-287,000,000	-331,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-240,000,000	-610,000,000
Net Amount After Deducting Gross Amounts Not Offset on the Balance Sheet From Net Amount of Assets (Liabilities) Presented on the Balance Sheet	129,000,000	197,000,000
Repurchase Agreements [Member] | Liability [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	49,729,000,000	63,533,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	49,729,000,000	63,533,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-4,773,000,000	-1,881,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-44,806,000,000	-61,652,000,000
Reverse Repurchase Agreements [Member] | Assets [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Gross Amount of Recognized Assets (Liabilities)	6,685,000,000	1,881,000,000
Net Amount of Assets (Liabilities) Presented on the Balance Sheet	6,685,000,000	1,881,000,000
Gross Amounts of Financial Instruments Not Offset on the Balance Sheet	-4,773,000,000	-1,881,000,000
Gross Amounts of Cash Collateral Not Offset on the Balance Sheet	-1,912,000,000	0
Net Amount After Deducting Gross Amounts Not Offset on the Balance Sheet From Net Amount of Assets (Liabilities) Presented on the Balance Sheet	0	0
Agency Securities [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Agency Securities Pledged As Collateral Amortized Cost	54,031,000,000	65,248,000,000
Agency Securities Pledged As Collateral Accrued Interest	150,000,000	178,000,000
Derivative [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	56,000,000	28,000,000
Available For Sale Securities Pledged As Collateral Accrued Interest	0	1,000,000
Restricted Cash and Cash Equivalents	224,000,000	41,000,000
Total Fair Value Of Agency Securities Pledged And Accrued Interest	351,000,000	140,000,000
Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	52,047,000,000	62,708,000,000
Variable Interest Entity, Primary Beneficiary [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	1,417,000,000	1,459,000,000
Available For Sale Securities Pledged As Collateral Accrued Interest	4,000,000	5,000,000
Total Fair Value Of Agency Securities Pledged And Accrued Interest	1,421,000,000	1,464,000,000
Under Prime Broker Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	519,000,000	91,000,000
Available For Sale Securities Pledged As Collateral Accrued Interest	1,000,000	0
Total Fair Value Of Agency Securities Pledged And Accrued Interest	564,000,000	148,000,000
Includes Sold But Not Yet Settled Securities [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	54,039,000,000	64,286,000,000
US Treasury Securities [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	196,000,000	3,778,000,000
US Treasury Securities [Member] | Derivative [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	71,000,000	70,000,000
US Treasury Securities [Member] | Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	125,000,000	3,708,000,000
Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available For Sale Securities Pledged As Collateral Accrued Interest	146,000,000	189,000,000
Total Fair Value Of Agency Securities Pledged And Accrued Interest	52,319,000,000	66,608,000,000
Excluding Cash Received [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Restricted Cash and Cash Equivalents	269,000,000	101,000,000
Under Prime Broker Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Restricted Cash and Cash Equivalents	44,000,000	57,000,000
Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Restricted Cash and Cash Equivalents	1,000,000	3,000,000
30 Days or Less [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	17,683,000,000	27,694,000,000
Agency Securities Pledged As Collateral Amortized Cost	17,858,000,000	28,125,000,000
Agency Securities Pledged As Collateral Accrued Interest	49,000,000	76,000,000
Maturity 31 To 59 Days [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	15,881,000,000	14,955,000,000
Agency Securities Pledged As Collateral Amortized Cost	16,024,000,000	15,210,000,000
Agency Securities Pledged As Collateral Accrued Interest	44,000,000	42,000,000
Maturity 60 To 90 Days [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	5,585,000,000	10,117,000,000
Agency Securities Pledged As Collateral Amortized Cost	5,630,000,000	10,290,000,000
Agency Securities Pledged As Collateral Accrued Interest	16,000,000	28,000,000
Maturity over 90 days [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	14,315,000,000	11,401,000,000
Agency Securities Pledged As Collateral Amortized Cost	14,519,000,000	11,623,000,000
Agency Securities Pledged As Collateral Accrued Interest	41,000,000	32,000,000
Maturity Overnight [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	125,000,000	3,708,000,000
Agency Securities Pledged As Collateral Amortized Cost	125,000,000	3,760,000,000
Agency Securities Pledged As Collateral Accrued Interest	0	16,000,000
Assets Pledged to Us [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	17,000,000	82,000,000
Restricted Cash and Cash Equivalents	183,000,000	366,000,000
Restricted Cash and Securities Pledged	6,914,000,000	2,460,000,000
Assets Pledged to Us [Member] | Derivative [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	17,000,000	82,000,000
Restricted Cash and Securities Pledged	240,000,000	612,000,000
Assets Pledged to Us [Member] | Reverse Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	6,658,000,000	1,848,000,000
Assets Pledged to Us [Member] | US Treasury Securities [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	6,714,000,000	2,012,000,000
Assets Pledged to Us [Member] | US Treasury Securities [Member] | Derivative [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	56,000,000	164,000,000
Assets Pledged to Us [Member] | Derivative [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Restricted Cash and Cash Equivalents	167,000,000	366,000,000
Assets Pledged to Us [Member] | Repurchase Agreements [Member]	'	'
Offsetting Assets and Liabilities [Line Items]	'	'
Restricted Cash and Cash Equivalents	$16,000,000	'

Pledged_Assets_Pledged_Assets_

Pledged Assets Pledged Assets (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	$53,589	$67,875
Available-for-sale Securities Pledged as Collateral	51,850	62,205
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	6,658	1,848
Available For Sale Securities Pledged As Collateral Accrued Interest	151	195
Restricted Cash and Cash Equivalents	269	101
Total Fair Value Of Agency Securities Pledged And Accrued Interest	54,655	68,360
Agency Securities Pledged As Collateral Amortized Cost	54,156	69,008
Agency Securities Pledged As Collateral Accrued Interest	'	194
Agency Securities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Agency Securities Pledged As Collateral Amortized Cost	54,031	65,248
Agency Securities Pledged As Collateral Accrued Interest	150	178
Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	52,047	62,708
Derivative [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	56	28
Available For Sale Securities Pledged As Collateral Accrued Interest	0	1
Restricted Cash and Cash Equivalents	224	41
Total Fair Value Of Agency Securities Pledged And Accrued Interest	351	140
US Treasury Securities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	196	3,778
US Treasury Securities [Member] | Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	125	3,708
US Treasury Securities [Member] | Derivative [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	71	70
Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available For Sale Securities Pledged As Collateral Accrued Interest	146	189
Total Fair Value Of Agency Securities Pledged And Accrued Interest	52,319	66,608
Variable Interest Entity, Primary Beneficiary [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	1,417	1,459
Available For Sale Securities Pledged As Collateral Accrued Interest	4	5
Total Fair Value Of Agency Securities Pledged And Accrued Interest	1,421	1,464
Under Prime Broker Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	519	91
Available For Sale Securities Pledged As Collateral Accrued Interest	1	0
Total Fair Value Of Agency Securities Pledged And Accrued Interest	564	148
Includes Sold But Not Yet Settled Securities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	54,039	64,286
Excluding Cash Received [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted Cash and Cash Equivalents	269	101
Under Prime Broker Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted Cash and Cash Equivalents	44	57
Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted Cash and Cash Equivalents	1	3
Maturity up to 30 days [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	17,683	27,694
Agency Securities Pledged As Collateral Amortized Cost	17,858	28,125
Agency Securities Pledged As Collateral Accrued Interest	49	76
Maturity 31 To 59 Days [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	15,881	14,955
Agency Securities Pledged As Collateral Amortized Cost	16,024	15,210
Agency Securities Pledged As Collateral Accrued Interest	44	42
Maturity 60 To 90 Days [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	5,585	10,117
Agency Securities Pledged As Collateral Amortized Cost	5,630	10,290
Agency Securities Pledged As Collateral Accrued Interest	16	28
Maturity over 90 days [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	14,315	11,401
Agency Securities Pledged As Collateral Amortized Cost	14,519	11,623
Agency Securities Pledged As Collateral Accrued Interest	41	32
Maturity Overnight [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Security Owned and Pledged as Collateral, Fair Value	125	3,708
Agency Securities Pledged As Collateral Amortized Cost	125	3,760
Agency Securities Pledged As Collateral Accrued Interest	0	16
Assets Pledged to Us [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	17	82
Restricted Cash and Cash Equivalents	183	366
Restricted Cash and Securities Pledged	6,914	2,460
Assets Pledged to Us [Member] | Derivative [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	17	82
Restricted Cash and Securities Pledged	240	612
Assets Pledged to Us [Member] | US Treasury Securities [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	6,714	2,012
Assets Pledged to Us [Member] | US Treasury Securities [Member] | Derivative [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	56	164
Assets Pledged to Us [Member] | Reverse Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Available-for-sale Securities Pledged as Collateral	6,658	1,848
Assets Pledged to Us [Member] | Derivative [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted Cash and Cash Equivalents	167	366
Assets Pledged to Us [Member] | Repurchase Agreements [Member]	'	'
Schedule of Trading Securities and Other Trading Assets [Line Items]	'	'
Restricted Cash and Cash Equivalents	$16	'

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
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	$54,960	$64,482
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	196	3,822
Derivative Assets	686	1,194
Other Long-term Debt	874	910
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	-6,658	-1,848
Derivative Instruments Not Designated as Hedging Instruments, Asset, at Fair Value	686	1,194
Marketable Securities, Equity Securities	352	237
Derivative Instruments Not Designated as Hedging Instruments, Liability, at Fair Value	417	422
Derivative Liabilities	417	422
Transfers between hierarchy levels	'0	'
Fair Value, Inputs, Level 1 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	'	-1,848
Fair Value, Inputs, Level 2 [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Other Long-term Debt	'	910
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	554	4,098
Liabilities, Fair Value Disclosure	6,658	1,848
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	57,057	67,096
Liabilities, Fair Value Disclosure	1,291	1,332
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | TBA and Forward Settling Agency Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative Assets	'	17
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Sale Of TBA And Forward Settling Agency Securities [Member]	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'
Derivative Assets	49	22
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [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	96	258
Interest Rate Swap [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	368	400
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [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	560	880
Interest Rate Swap [Member] | Derivative liabilities, 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	368	400
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	56,377	65,941
US Treasury Securities [Member] | Future [Member] | Fair Value, Inputs, Level 1 [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	($6)	$39

Management_Agreement_and_Relat

Management Agreement and Related Party Transactions (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Related Party Transaction [Line Items]	'	'
Management Fee Expense	$29	$33

Income_Taxes_Details

Income Taxes (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2014	Mar. 31, 2013
Investments, Owned, Federal Income Tax Note [Line Items]	'	'
Dividends, Common Stock, Cash	($229)	($496)

Stockholders_Equity_Summary_of

Stockholders' Equity (Summary of Follow-on Public Offerings of Common Stock) (Details) (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Variable Interest Entity, Measure of Activity, Expense	($3)	'	$13	'
Common Stock, Shares, Issued	352.8	356.2	'	'
Stock Issued During Period, Value, New Issues	'	'	1,802	'
Stock Repurchase Program, Authorized Amount	1,000	1,000	'	500
Stock Repurchased During Period, Shares	-3.4	'	'	'
Treasury Stock Acquired, Average Cost Per Share	$22.10	'	'	'
Stock Repurchased During Period, Value	-74	'	'	'
Stock Repurchase Program, Remaining Authorized Repurchase Amount	992	'	'	'
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	521	'	-837	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	43	'	49	'
Total Reclass of Other Comprehensive Income	62	'	75	'
Other comprehensive income (loss)	564	'	-788	'
Proceeds from Issuance of Common Stock	0	'	1,802	'
Accumulated Other Comprehensive Income (Loss), Net of Tax	-819	-1,383	767	1,555
Common Stock [Member]	'	'	'	'
Stock Issued During Period, Value, New Issues	'	'	1	'
Stock Repurchased During Period, Shares	-3.4	'	'	'
Stock Repurchased During Period, Value	-74	'	'	'
Public offering of common stock	'	'	57.6	'
Agency Securities [Member]	'	'	'	'
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-566	-1,087	1,203	2,040
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	502	'	-863	'
Other Comprehensive Income Reclassification Adjustment For Sale Of Security Reversal Of Prior Period Unrealized Gain And Losses On Realization	19	'	26	'
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	43	'	49	'
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	($253)	$296	($436)	$485

Stockholders_Equity_Details

Stockholders' Equity (Details) (USD $)	3 Months Ended				12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2013
Common Stock, Shares, Issued	352.8	356.2	'	'	356.2
Proceeds from Issuance of Common Stock	$0	'	$1,802	'	'
Spread Over LIBOR	'43	'	'	'	'42
Issuance of common stock, value	'	'	1,802	'	'
Stock Repurchase Program, Authorized Amount	1,000	1,000	'	500	'
Stock Repurchased During Period, Shares	-3.4	'	'	'	'
Treasury Stock Acquired, Average Cost Per Share	$22.10	'	'	'	'
Stock Repurchased During Period, Value	-74	'	'	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	43	'	49	'	'
Total Reclass of Other Comprehensive Income	62	'	75	'	'
Accumulated Other Comprehensive Income (Loss), Net of Tax	-819	-1,383	767	1,555	-1,383
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	521	'	-837	'	'
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	564	'	-788	'	'
Agency Securities [Member]	'	'	'	'	'
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax	-566	-1,087	1,203	2,040	-1,087
Other Comprehensive Income Reclassification Adjustment For Sale Of Security Reversal Of Prior Period Unrealized Gain And Losses On Realization	19	'	26	'	'
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	502	'	-863	'	'
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	43	'	49	'	'
Deferred Gain (Loss) on Discontinuation of Interest Rate Fair Value Hedge	-253	296	-436	485	296
Interest Rate Swap [Member] | Agency Securities [Member]	'	'	'	'	'
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	502	'	-863	'	'
Forward Contracts [Member] | Interest Rate Swap [Member]	'	'	'	'	'
Notional Amount	'	4,000	'	'	4,000
Interest Rate Swap [Member]	'	'	'	'	'
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax	$0	'	$0	'	'

Subsequent_Event_Details

Subsequent Event (Details) (USD $)	12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Dec. 31, 2013	5-May-14	Mar. 31, 2014
Subsequent Event [Line Items]	'	'	'
Preferred Stock, Liquidation Preference Per Share	'	$25	'
Preferred Stock, Value, Issued	$167	'	$167
Preferred Stock, Dividend Rate, Percentage	8.00%	'	'
Preferred Stock, Shares Issued	6.9	'	6.9
Preferred Class B [Member]	'	'	'
Subsequent Event [Line Items]	'	'	'
Share Price	'	$24.21	'
Preferred Stock, Value, Issued	'	$169	'
Preferred Stock, Dividend Rate, Percentage	7.75%	'	'
Preferred Stock, Shares Issued	'	7	'
Preferred Class B [Member] | Preferred Class B [Member]	'	'	'
Subsequent Event [Line Items]	'	'	'
Preferred Stock, Shares Issued	'	1	'