AGNC Investment (AGNC) 10-Q 6 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 30, 2015
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Entity Registrant Name	American Capital Agency Corp
Entity Central Index Key	1423689
Entity Filer Category	Large Accelerated Filer
Current Fiscal Year End Date	-19
Entity Common Stock, Shares Outstanding		352,788,707
Trading Symbol	AGNC

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Assets:
Agency securities, at fair value (including pledged securities of $56,836 and $51,629, respectively)	$60,131	$55,482
Agency securities transferred to consolidated variable interest entities, at fair value (pledged securities)	1,221	1,266
U.S. Treasury securities, at fair value (including pledged securities of $4,328 and $2,375, respectively)	4,328	2,427
REIT equity securities, at fair value	68	68
Cash and cash equivalents	1,708	1,720
Restricted cash	1,108	713
Derivative assets, at fair value	229	408
Receivable for securities sold (including pledged securities of $721 and $79, respectively)	908	239
Receivable under reverse repurchase agreements	3,175	5,218
Other assets	229	225
Total assets	73,105	67,766
Liabilities:
Repurchase agreements	58,112	50,296
Debt of consolidated variable interest entities, at fair value	725	761
Payable for agency securities purchased	50	843
Derivative liabilities, at fair value	1,352	890
Dividend payable	85	85
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	3,363	5,363
Accounts payable and other accrued liabilities	62	100
Total liabilities	63,749	58,338
Stockholders' equity:
Preferred stock - $0.01 par value; 10.0 shares authorized: Redeemable Preferred Stock; $0.01 par value; 6.9 shares issued and outstanding (aggregate liquidation preference of $348 and $173, respectively)	336	336
Common stock - $0.01 par value; 600.0 shares authorized; 352.8 and 356.2 shares issued and outstanding, respectively	4	4
Additional paid-in capital	10,332	10,332
Retained deficit	-2,166	-1,674
Accumulated other comprehensive income	850	430
Total stockholders' equity	9,356	9,428
Total liabilities and stockholders' equity	$73,105	$67,766

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parentheticals) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, except Per Share data, unless otherwise specified
Statement of Financial Position [Abstract]
Available-for-sale Securities Pledged as Collateral	$56,836	$51,629
Trading Securities Pledged as Collateral	4,328	2,375
Assets Pledged included in Receivable for Securities Sold	721	79
Preferred Stock, Par or Stated Value Per Share (in dollars 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
Preferred Stock Liquidation Preference	$348	$348
Common Stock, Par or Stated Value Per Share (in dollars per share)	$0.01	$0.01
Common Stock, Shares Authorized	600	600
Common Stock, Shares, Issued	352.8	352.8
Common Stock, Shares, Outstanding	352.8	352.8

Consolidated_Statements_Of_Com

Consolidated Statements Of Comprehensive Income (USD $)	3 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Interest income:
Interest income	$383	$399
Interest expense	86	108
Net interest income	297	291
Other income, net:
Gain (loss) on sale of agency securities, net	36	-19
Loss on derivative instruments and other securities, net	-549	-378
Total other income, net	-513	-397
Expenses:
Management fees	30	29
General and administrative expenses	6	6
Total expenses	36	35
Net loss	-252	-141
Dividend on preferred stock	7	3
Net loss attributable to common stockholders	-259	-144
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	391	521
Unrealized gain on derivative instruments, net	29	43
Other comprehensive income (loss)	420	564
Comprehensive income	168	423
Comprehensive income available to common stockholders	$161	$420
Weighted average number of common shares outstanding-basic and diluted (shares)	352.8	354.8
Net loss per common share - basic and diluted (dollars per share)	($0.73)	($0.41)
Comprehensive income per common share - basic and diluted	$0.46	$1.18
Dividends declared per common share	$0.66	$0.65

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, 2013	$8,697	$167	$4	$10,406	($497)	($1,383)
Balance, Common Stock, shares at Dec. 31, 2013			356.2
Balance, Preferred Stock, shares at Dec. 31, 2013		6.9
Net income (loss)	-141				-141
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	521					521
Amounts reclassified from accumulated OCI	43					43
Repurchase of common stock	-74			-74
Repurchase of common stock shares			-3.4
Preferred dividends declared	-3				-3
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
Balance, Preferred Stock, shares at Mar. 31, 2014		6.9
Balance, value at Dec. 31, 2014	9,428	336	4	10,332	-1,674	430
Balance, Common Stock, shares at Dec. 31, 2014	352.8		352.8
Balance, Preferred Stock, shares at Dec. 31, 2014	6.9	6.9
Net income (loss)	-252				-252
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	391					391
Amounts reclassified from accumulated OCI	29					29
Repurchase of common stock shares			-3.4
Preferred dividends declared	-7				-7
Common dividends declared	-233				-233
Balance, value at Mar. 31, 2015	$9,356	$336	$4	$10,332	($2,166)	$850
Balance, Common Stock, shares at Mar. 31, 2015	352.8		352.8
Balance, Preferred Stock, shares at Mar. 31, 2015	6.9	6.9

Consolidated_Statements_Of_Cas

Consolidated Statements Of Cash Flows (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net income (loss)	($252)	($141)
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of agency securities premiums and discounts, net	133	142
Amortization of accumulated other comprehensive loss on interest rate swaps de-designated as qualifying hedges	29	43
(Gain) loss on sale of agency securities, net	36	-19
Loss on derivative instruments and other securities, net	549	378
(Increase) decrease in other assets	-4	60
Increase (decrease) in accounts payable and other accrued liabilities	1	-13
Net cash provided by operating activities	420	488
Investing activities:
Purchases of agency securities	-14,672	-1,403
Proceeds from sale of agency securities	7,099	9,545
Principal collections on agency securities	1,811	1,853
Purchases of U.S. Treasury securities	-21,929	-4,343
Proceeds from sale of U.S. Treasury securities	17,999	12,807
Net proceeds from (payments on) reverse repurchase agreements	2,043	-4,804
Net proceeds from other derivative instruments	99	58
Purchases of REIT equity securities	-11	-204
Proceeds from sale of REIT equity securities	11	86
Increase in restricted cash	-395	-168
Other investing cash flows, net	-28	-183
Net cash (used in) provided by investing activities	-7,973	13,244
Financing activities:
Proceeds from repurchase arrangements, net	120,104	79,314
Repayments on repurchase agreements	-112,288	-93,118
Repayments on debt of consolidated variable interest entities	-35	-36
Payments made on common stock repurchases	0	-74
Cash dividends paid	-240	-235
Net cash provided by (used in) financing activities	7,541	-14,149
Net change in cash and cash equivalents	-12	-417
Cash and cash equivalents at beginning of period	1,720	2,143
Cash and cash equivalents at end of period	$1,708	$1,726

Interim_Consolidated_Financial

Interim Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2015
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 subsidiaries, American Capital Agency TRS, LLC and Old Georgetown Insurance Co., 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, 2015
Organization, Consolidation and Presentation of Financial Statements [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 generate attractive risk-adjusted returns for distribution to our stockholders through regular monthly dividends from the combination of our net interest income and net realized gains and losses on our investments and hedging activities while preserving our net asset value (also referred to as "net book value," "NAV" and "stockholders' equity"). 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, 2015
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 valuations obtained from third-party pricing services and non-binding dealer quotes derived from common market pricing methods using observable (or "Level 2") inputs. 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 based on a market approach using quoted market prices (or "Level 1" inputs). 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 exists 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.
	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 effective 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. 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.
	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 in the "to-be-announced" market on a generic pool basis ("TBA securities") 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 may also 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 derivative instruments 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, with swap agreements entered into subsequent to May 2013 subject to central clearing 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" interest rate swaps based on valuations obtained from third-party pricing services and the swap counterparty (collectively, “third-party valuations”). The third-party valuations are model-driven using observable inputs consisting of LIBOR and the forward yield curve. We also consider the creditworthiness of both us and our counterparties and the impact of netting and credit enhancement provisions contained in each derivative agreement, such as collateral postings. All of our "non-centrally cleared" interest rate swaps are subject to bilateral collateral arrangements. Consequently, no credit valuation adjustment was made in determining the fair value of such instruments.
	Interest rate swaptions
	We purchase interest rate swaptions generally to help mitigate the potential impact of larger, more rapid changes in interest rates on the performance of our investment portfolio. 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 our interest rate swaption agreements based on model-driven valuations obtained from third-party pricing services and the swaption counterparty using observable inputs, taking into account 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, 2015
Investments, Debt and Equity Securities [Abstract]
Investment Securities	Investment Securities
	As of March 31, 2015 and December 31, 2014, our investment portfolio consisted of $61.4 billion and $56.7 billion of agency MBS, respectively, and a $4.9 billion and $14.8 billion net long TBA position, at fair value, respectively.
	Our TBA positions are reported at their net carrying value of $79 million and $192 million as of March 31, 2015 and December 31, 2014, respectively, in derivative assets/(liabilities) on our accompanying consolidated balance sheets. The net carrying value of our TBA position represents the difference between the fair value of the underlying agency security in the TBA contract and the cost basis or the forward price to be paid or received for the underlying agency security. (See Note 6 for further details of our net TBA position as of March 31, 2015 and December 31, 2014.)
	As of March 31, 2015 and December 31, 2014, the net unamortized premium balance on our agency MBS was $2.6 billion and $2.5 billion, respectively, including interest and principal-only strips.
	The following tables summarize our investments in agency MBS as of March 31, 2015 and December 31, 2014 (dollars in millions):
			31-Mar-15
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	58,235		$	977			$	(72	)		$	59,140
	Adjustable rate		622			20				—				642
	CMO		1,138			35				—				1,173
	Interest-only and principal-only strips		354			46				(3		)		397
	Total agency MBS		$	60,349		$	1,078			$	(75	)		$	61,352
			December 31, 2014
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	53,945		$	715			$	(187	)		$	54,473
	Adjustable rate		659			19				—				678
	CMO		1,172			24				(1		)		1,195
	Interest-only and principal-only strips		372			33				(3		)		402
	Total agency MBS		$	56,148		$	791			$	(191	)		$	56,748
			31-Mar-15
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	44,954		$	12,231			$	289			$	57,474
	Unamortized discount		(36		)	(5		)		—				(41		)
	Unamortized premium		1,944			606				12				2,562
	Amortized cost		46,862			12,832				301				59,995
	Gross unrealized gains		823			205				4				1,032
	Gross unrealized losses		(49		)	(23		)		—				(72		)
	Total available-for-sale agency MBS, at fair value		47,636			13,014				305				60,955
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		331			23				—				354
	Gross unrealized gains		43			3				—				46
	Gross unrealized losses		(2		)	(1		)		—				(3		)
	Total agency MBS remeasured at fair value through earnings		372			25				—				397
	Total agency MBS, at fair value		$	48,008		$	13,039			$	305			$	61,352
	Weighted average coupon as of March 31, 2015 2		3.55		%	3.7		%		3.16		%		3.58		%
	Weighted average yield as of March 31, 2015 3		2.63		%	2.71		%		1.61		%		2.64		%
	Weighted average yield for the quarter ended March 31, 2015 3		2.56		%	2.58		%		1.63		%		2.57		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.1 billion and the weighted average contractual interest we are entitled to receive was 5.45% of this amount as of March 31, 2015. The par value of our principal-only agency MBS strips was $235 million as of March 31, 2015.
	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, 2015.
	3	Incorporates a weighted average future constant prepayment rate assumption of 10% based on forward rates as of March 31, 2015.
			December 31, 2014
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	42,749		$	10,566			$	107			$	53,422
	Unamortized discount		(37		)	(5		)		—				(42		)
	Unamortized premium		1,880			514				2				2,396
	Amortized cost		44,592			11,075				109				55,776
	Gross unrealized gains		610			145				3				758
	Gross unrealized losses		(127		)	(61		)		—				(188		)
	Total available-for-sale agency MBS, at fair value		45,075			11,159				112				56,346
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		348			24				—				372
	Gross unrealized gains		30			3				—				33
	Gross unrealized losses		(2		)	(1		)		—				(3		)
	Total agency MBS remeasured at fair value through earnings		376			26				—				402
	Total agency MBS, at fair value		$	45,451		$	11,185			$	112			$	56,748
	Weighted average coupon as of December 31, 2014 2		3.63		%	3.7		%		3.52		%		3.65		%
	Weighted average yield as of December 31, 2014 3		2.75		%	2.73		%		1.87		%		2.74		%
Weighted average yield for the year ended December 31, 2014 3		2.62		%	2.64		%		1.66		%		2.63		%
________________________
1	The underlying UPB of our interest-only agency MBS strips was $1.2 billion and the weighted average contractual interest we are entitled to receive was 5.46% of this amount as of December 31, 2014. The par value of our principal-only agency MBS strips was $242 million as of December 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 December 31, 2014.
3	Incorporates a weighted average future constant prepayment rate assumption of 9% based on forward rates as of December 31, 2014.
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, 2015 and December 31, 2014, our weighted average expected constant prepayment rate ("CPR") over the remaining life of our aggregate agency MBS portfolio was 10% and 9%, respectively. Our estimates differ materially for different types of securities and thus individual holdings have a wide range of projected CPRs.
The following table summarizes our agency MBS classified as available-for-sale as of March 31, 2015 and December 31, 2014 according to their estimated weighted average life classification (dollars in millions):
		31-Mar-15											December 31, 2014
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 and ≤ 3 years		1,049			1,032				3.36%		1.64%		289			280		4.08%		2.62%
> 3 years and ≤ 5 years		23,885			23,373				3.27%		2.37%		22,153			21,820		3.26%		2.40%
> 5 years and ≤10 years		35,898			35,471				3.64%		2.80%		33,271			33,055		3.73%		2.92%
> 10 years		123			119				3.75%		3.28%		633			621		3.28%		3.15%
Total		$	60,955		$	59,995			3.49%		2.61%		$	56,346		$	55,776	3.54%		2.72%
_______________________
1	Excludes interest and principal-only strips.
The weighted average life of our interest-only strips was 5.7 and 6.0 years as of March 31, 2015 and December 31, 2014, respectively. The weighted average life of our principal-only strips was 7.6 and 8.1 years as of March 31, 2015 and December 31, 2014, 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, 2015 and 2014 (in millions):
Agency Securities Classified as		Beginning Accumulated OCI			Unrealized			Reversal of			Ending
Available-for-Sale		Balance			Gains and (Losses), Net			Unrealized			Accumulated
								(Gains) and Losses,			OCI
								Net on Realization			Balance
Three months ended March 31, 2015		$	570		427			(36	)		$	961
Three months ended March 31, 2014		$	(1,087	)	502			19			$	(566	)
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, 2015 and December 31, 2014 (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, 2015		$	542		$	(3	)		$	7,942			$	(69	)	$	8,484	$	(72	)
December 31, 2014		$	778		$	(2	)		$	11,679			$	(186	)	$	12,457	$	(188	)
As of the end of each respective reporting period, 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. We did not recognize any OTTI charges on our investment securities for the three months ended March 31, 2015 and 2014. 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, 2015 and 2014 (in millions):
		Three Months Ended March 31,
Agency Securities Classified as		2015			2014
Available-for-Sale
Agency MBS sold, at cost		$	(7,732	)	$	(9,711	)
Proceeds from agency MBS sold 1		7,768			9,692
Net gain (loss) on sale of agency MBS		$	36		$	(19	)
Gross gain on sale of agency MBS		$	57		$	42
Gross loss on sale of agency MBS		(21		)	(61		)
Net gain (loss) on sale of agency MBS		$	36		$	(19	)
________________________
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, 2015 and 2014, we recognized a net unrealized gain of $11 million and $12 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, 2015 and December 31, 2014, 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 $1.2 billion and $1.3 billion as of March 31, 2015 and December 31, 2014, respectively, and debt, at fair value, of $725 million and $761 million, respectively, in our accompanying consolidated balance sheets. As of March 31, 2015 and December 31, 2014, the agency securities had an aggregate unpaid principal balance of $1.1 billion and $1.2 billion, respectively, and the debt had an aggregate unpaid principal balance of $707 million and $742 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, 2015, we recorded no gain or loss associated with our consolidated debt. For the three months ended March 31, 2014, we recognized a net loss of $(3) million 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 both March 31, 2015 and December 31, 2014, the fair value of our CMO securities and interest and principal-only securities was $1.6 billion, excluding the consolidated CMO trusts discussed above, or $2.1 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 $289 million and $274 million as of March 31, 2015 and December 31, 2014, respectively.

Repurchase_Agreements_And_Othe

Repurchase Agreements And Other Debt	3 Months Ended
	Mar. 31, 2015
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. For additional information regarding our pledged assets please refer to 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, 2015, we had 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, 2015 and December 31, 2014 (dollars in millions):
		31-Mar-15					December 31, 2014
	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	$	24,680	0.36	%	16	$	14,157	0.37	%	15
	> 1 to ≤ 3 months	15,100		0.38	%	52	20,223		0.38	%	61
	> 3 to ≤ 6 months	5,455		0.43	%	132	6,654		0.42	%	120
	> 6 to ≤ 9 months	2,668		0.56	%	222	1,575		0.5	%	225
	> 9 to ≤ 12 months	1,826		0.47	%	330	2,678		0.54	%	313
	> 12 to ≤ 24 months	700		0.61	%	491	600		0.57	%	551
	> 24 to ≤ 36 months	852		0.61	%	937	952		0.6	%	999
	> 36 to ≤ 48 months	1,150		0.68	%	1,268	650		0.64	%	1,266
	> 48 to < 60 months	1,900		0.7	%	1,706	900		0.68	%	1,542
	Total agency MBS	54,331		0.41	%	164	48,389		0.41	%	143
	U.S. Treasury securities:
	1 day	3,781		0.21	%	1	1,907		0.09	%	1
	Total / Weighted Average	$	58,112	0.33	%	142	$	50,296	0.4	%	138
	As of March 31, 2015 and December 31, 2014, debt of consolidated VIEs, at fair value ("other debt") was $725 million and $761 million, respectively. As of March 31, 2015 and December 31, 2014, our other debt had a weighted average interest rate of LIBOR plus 43 basis points and a principal balance of $707 million and $742 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, 2015 and December 31, 2014 was 5.6 and 5.8 years, respectively.
	As of March 31, 2015 and December 31, 2014, 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 total "at risk" leverage. However, pursuant to ASC 815, we account for such transactions as one or more series of derivative transactions and, consequently, they are not recognized as debt on our consolidated balance sheet and are excluded from commensurate measurements of our balance sheet debt to equity leverage ratios.

Derivative_and_Other_Hedging_I

Derivative and Other Hedging Instruments	3 Months Ended
	Mar. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [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 and purchase or short TBA and U.S. Treasury securities. We may also 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, 2015 and 2014, we reclassified $29 million and $43 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 was $113 million and $126 million, respectively. The difference of $84 million and $83 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, 2015, the remaining net deferred loss in accumulated OCI related to de-designated interest rate swaps was $111 million and will be reclassified from OCI into interest expense over a remaining weighted average period of 1.2 years. As of March 31, 2015, the net deferred loss expected to be reclassified from OCI into interest expense over the next twelve months was $91 million.
	Derivative and Other Hedging Instrument Assets (Liabilities), at Fair Value
	The table below summarizes fair value information about our derivative and other hedging instrument assets and liabilities as of March 31, 2015 and December 31, 2014 (in millions):
	Derivative and Other Hedging Instruments		Balance Sheet Location		March 31, 2015				December 31, 2014
	Interest rate swaps		Derivative assets, at fair value		$	70			$	136
	Swaptions		Derivative assets, at fair value		50				75
	TBA securities		Derivative assets, at fair value		109				197
	Total				$	229			$	408
	Interest rate swaps		Derivative liabilities, at fair value		$	(1,308	)		$	(880	)
	TBA securities		Derivative liabilities, at fair value		(30		)		(5		)
	U.S. Treasury futures - short		Derivative liabilities, at fair value		(14		)		(5		)
	Total				$	(1,352	)		$	(890	)
	U.S. Treasury securities - long		U.S. Treasury securities, at fair value		$	4,328			$	2,427
	U.S. Treasury securities - short		Obligation to return securities borrowed under reverse repurchase agreements, at fair value 1		(3,363		)		(5,363		)
	Total - (short)/long, net				$	965			$	(2,936	)
	________________________
	1	Our obligation to return securities borrowed under reverse repurchase agreements as of March 31, 2015 and December 31, 2014 relates to securities borrowed to cover short sales of U.S. Treasury securities from which we received total sale proceeds of $3.3 billion and $5.4 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, 2015 and December 31, 2014 (dollars in millions):
			31-Mar-15
	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		$	14,850			1.21%		0.24%		$	(110	)		1.9
	> 3 to ≤ 5 years		10,475				1.74%		0.26%		(149		)		4.3
	> 5 to ≤ 7 years		7,050				2.61%		0.26%		(309		)		6.2
	> 7 to ≤ 10 years		9,825				2.45%		0.26%		(405		)		8.2
	> 10 years		2,725				3.15%		0.26%		(265		)		12.5
	Total Payer Interest Rate Swaps		$	44,925			1.94%		0.25%		$	(1,238	)		5.2
	________________________
	1	Notional amount includes forward starting swaps of $10.1 billion with an average forward start date of 0.9 years and an average maturity of 7.3 years from March 31, 2015.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.64% as of March 31, 2015.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from March 31, 2015 through stated maturity date.
			December 31, 2014
	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		$	12,300			1.33%		0.21%		$	(87	)		2
	> 3 to ≤ 5 years		8,975				1.63%		0.24%		(4		)		4.2
	> 5 to ≤ 7 years		7,250				2.47%		0.23%		(139		)		6.1
	> 7 to ≤ 10 years		10,775				2.48%		0.24%		(223		)		8.3
	> 10 years		4,400				3.19%		0.23%		(291		)		12.6
	Total Payer Interest Rate Swaps		$	43,700			2.05%		0.23%		$	(744	)		5.8
	________________________
	1	Notional amount includes forward starting swaps of $12.4 billion with an average forward start date of 1.1 years and an average maturity of 7.9 years from December 31, 2014.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.68% as of December 31, 2014.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from December 31, 2014 through stated maturity date.
	The following table summarizes our interest rate payer swaption agreements outstanding as of March 31, 2015 and December 31, 2014 (dollars in millions):
	Payer Swaptions		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)
	31-Mar-15
	≤ 1 year		$	117			$	28			7		$	4,650			3.33%		3M		7.1
	> 1 to ≤ 2 years		13				1				16		550				4.01%		3M		5.7
	Total Payer Swaptions		$	130			$	29			8		$	5,200			3.40%		3M		7
	31-Dec-14
	≤ 1 year		$	113			$	36			6		$	5,600			3.15%		3M		6.4
	> 1 to ≤ 2 years		32				10				16		1,200				3.87%		3M		5.1
	Total Payer Swaptions		$	145			$	46			8		$	6,800			3.28%		3M		6.2
The following table summarizes our interest rate receiver swaption agreements outstanding as of March 31, 2015 and December 31, 2014 (dollars in millions):
Receiver Swaptions		Option										Underlying Receiver Swap
Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Receive		Average		Average
						Value				Months to		Amount				Rate		Pay		Term
										Expiration								Rate		(Years)
																		(LIBOR)
31-Mar-15
≤ 1 year		$	6			$	21			2		$	750			1.96%		3M		6.7
31-Dec-14
≤ 1 year		$	18			$	29			5		$	4,250			1.78%		3M		6.4
The following table summarizes our U.S. Treasury securities as of March 31, 2015 and December 31, 2014 (in millions):
		31-Mar-15												31-Dec-14
Maturity		Face Amount Net Long / (Short)				Cost Basis				Market Value				Face Amount Net Long / (Short)				Cost Basis			Market Value
3 years		$	(900	)		$	(899	)		$	(902	)		$	—			$	—		$	—
5 years		(2,111		)		(2,096		)		(2,116		)		(4,674		)		(4,650		)	(4,645		)
7 years		(339		)		(334		)		(341		)		(717		)		(717		)	(718		)
10 years		4,258				4,303				4,324				2,410				2,422			2,427
Total U.S. Treasury securities, net		$	908			$	974			$	965			$	(2,981	)		$	(2,945	)	$	(2,936	)
The following tables summarize our TBA securities as of March 31, 2015 and December 31, 2014 (in millions):
		31-Mar-15																31-Dec-14
TBA Securities by Coupon		Notional				Cost				Market				Net Carrying Value 4				Notional			Cost			Market			Net Carrying Value 4
		Amount - Long (Short) 1				Basis 2				Value 3								Amount - Long (Short) 1			Basis 2			Value 3
15-Year TBA securities:
2.50%		$	1,632			$	1,670			$	1,673			$	3			$	962		$	968		$	980		$	12
3.00%		(2,733		)		(2,852		)		(2,866		)		(14		)		2,779			2,889			2,888			(1		)
3.50%		(192		)		(201		)		(203		)		(2		)		(468		)	(495		)	(494		)	1
4.00%		—				—				—				—				(13		)	(14		)	(14		)	—
Total 15-Year TBAs		(1,293		)		(1,383		)		(1,396		)		(13		)		3,260			3,348			3,360			12
30-Year TBA securities:
3.00%		5,432				5,500				5,566				66				5,254			5,259			5,313			54
3.50%		3,423				3,560				3,598				38				7,902			8,151			8,232			81
4.00%		(2,689		)		(2,862		)		(2,874		)		(12		)		(1,853		)	(2,019		)	(1,974		)	45
4.50%		—				—				—				—				(151		)	(163		)	(163		)	—
Total 30-Year TBAs		6,166				6,198				6,290				92				11,152			11,228			11,408			180
Total net TBA securities		$	4,873			$	4,815			$	4,894			$	79			$	14,412		$	14,576		$	14,768		$	192
		31-Mar-15																31-Dec-14
TBA Securities by Issuer		Notional				Cost				Market				Net Carrying Value 4				Notional			Cost			Market			Net Carrying Value 4
		Amount - Long (Short) 1				Basis 2				Value 3								Amount - Long (Short) 1			Basis 2			Value 3
Fannie Mae		$	2,230			$	2,125			$	2,178			$	53			$	15,127		$	15,316		$	15,509		$	193
Freddie Mac		(957		)		(1,021		)		(1,025		)		(4		)		(715		)	(740		)	(741		)	(1		)
Ginnie Mae		3,600				3,711				3,741				30				—			—			—			—
TBA securities, net		$	4,873			$	4,815			$	4,894			$	79			$	14,412		$	14,576		$	14,768		$	192
_____________________
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.
Gain (Loss) From Derivative Instruments and Other Securities, Net
The tables below summarize changes in our derivative and other hedge portfolio and their effect on our consolidated statements of comprehensive income for the three months ended March 31, 2015 and 2014 (in millions):
		Three Months Ended March 31, 2015
Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount					Amount of
		Long/(Short)							Expiration or			Long/(Short) March 31, 2015					Gain/(Loss)
		31-Dec-14							Exercise								Recognized in
																	Income on
																	Derivatives 1
TBA securities, net		$	14,412			45,500			(55,039	)		$	4,873				$	234
Interest rate swaps		$	(43,700	)		(3,500	)		2,275			$	(44,925	)			(746		)
Payer swaptions		$	(6,800	)		—			1,600			$	(5,200	)			(17		)
Receiver swaptions		$	4,250			—			(3,500	)		$	750				17
U.S. Treasury securities - short position		$	(5,392	)		(4,173	)		6,212			$	(3,353	)			(82		)
U.S. Treasury securities - long position		$	2,411			15,562			(13,712	)		$	4,261				52
U.S. Treasury futures contracts - short position		$	(730	)		(730	)		730			$	(730	)			(20		)
																	$	(562	)
________________________________
1	Excludes a net gain of $2 million from investments in REIT equity securities and a net gain of $11 million from interest and principal-only securities recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
		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
TBA securities, net		$	2,119			24,376			(12,586	)		$	13,909				$	60
Interest rate swaps		$	(43,250	)		(5,900	)		2,750			$	(46,400	)			(380		)
Payer swaptions		$	(14,250	)		(1,000	)		7,250			$	(8,000	)			(105		)
Receiver swaptions		$	—			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 from 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.

Pledged_Assets

Pledged Assets	3 Months Ended
	Mar. 31, 2015
Pledged Assets [Abstract]
Pledged Assets	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 swap agreements 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 registered clearinghouses, 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 the clearing exchanges' 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, 2015, 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, 2015, 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, 2015 and December 31, 2014 (in millions):
			March 31, 2015
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	57,245	$	1,221	$	171	$	141		$	58,778
	U.S. Treasury securities - fair value		3,789		—		539		—			4,328
	Accrued interest on pledged securities		176		4		2		—			182
	Restricted cash		29		—		1,077		2			1,108
	Total		$	61,239	$	1,225	$	1,789	$	143		$	64,396
			December 31, 2014
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	50,858	$	1,266	$	69	$	702		$	52,895
	U.S. Treasury securities - fair value		1,904		—		550		—			2,454
	Accrued interest on pledged securities		147		4		2		—			153
	Restricted cash		6		—		698		9			713
	Total		$	52,915	$	1,270	$	1,319	$	711		$	56,215
	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 other debt of consolidated VIEs by remaining maturity of the repurchase agreement and other debt liability, including securities pledged related to sold but not yet settled securities, as of March 31, 2015 and December 31, 2014 (in millions). For the corresponding repurchase agreement and other debt liability associated with the following amounts and the interest rates thereon, refer to Note 5.
			March 31, 2015						December 31, 2014
	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		$	25,572	$	25,188	$	69	$	14,605		$	14,453		$	41
	> 30 and ≤ 60 days		11,932		11,731		32		10,912			10,789			30
	> 60 and ≤ 90 days		3,937		3,880		11		10,205			10,109			28
	> 90 days		17,025		16,728		47		16,402			16,227			47
	Total agency MBS		58,466		57,527		159		52,124			51,578			146
	U.S. Treasury securities:
	1 day		3,789		3,774		21		1,904			1,899			5
	Total		$	62,255	$	61,301	$	180	$	54,028		$	53,477		$	151
	As of March 31, 2015 and December 31, 2014, 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, 2015 and December 31, 2014, we had assets pledged to us from counterparties as collateral under our reverse repurchase and derivative agreements summarized in the tables below (in millions).
			March 31, 2015						December 31, 2014
	Assets Pledged to AGNC		Reverse Repurchase Agreements		Derivative Agreements		Total		Reverse Repurchase Agreements			Derivative Agreements			Total
	Agency MBS - fair value		$	—	$	14	$	14	$	—		$	43		$	43
	U.S. Treasury securities - fair value		3,363		—		3,363		5,363			47			5,410
	Cash		—		—		—		—			28			28
	Total		$	3,363	$	14	$	3,377	$	5,363		$	118		$	5,481
	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, 2015 and December 31, 2014 (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-15
	Interest rate swap and swaption agreements, at fair value 1		$	120	$	—	$	120	$	(97	)	$	(14	)	$	9
	Receivable under reverse repurchase agreements		3,175		—		3,175		(3,175		)	—			—
	Total derivative, other hedging instruments and other assets		$	3,295	$	—	$	3,295	$	(3,272	)	$	(14	)	$	9
	31-Dec-14
	Interest rate swap and swaption agreements, at fair value 1		$	211	$	—	$	211	$	(94	)	$	(83	)	$	34
	Receivable under reverse repurchase agreements		5,218		—		5,218		(4,690		)	(528		)	—
Total derivative, other hedging instruments and other assets		$	5,429	$	—	$	5,429	$	(4,784	)	$	(611	)	$	34
		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-15
Interest rate swap agreements, at fair value 1		$	1,308	$	—	$	1,308	$	(97	)	$	(1,208	)	$	3
Repurchase agreements		58,112		—		58,112		(3,175		)	(54,937		)	—
Total derivative, other hedging instruments and other liabilities		$	59,420	$	—	$	59,420	$	(3,272	)	$	(56,145	)	$	3
31-Dec-14
Interest rate swap agreements, at fair value 1		$	880	$	—	$	880	$	(94	)	$	(782	)	$	4
Repurchase agreements		50,296		—		50,296		(4,690		)	(45,606		)	—
Total derivative, other hedging instruments and other liabilities		$	51,176	$	—	$	51,176	$	(4,784	)	$	(46,388	)	$	4
_______________________
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.

Fair_Value_Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	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 from 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, 2015. 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, 2015 and December 31, 2014 (in millions):
			March 31, 2015						December 31, 2014
			Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	Assets:
	Agency securities		$	—	$	60,131	$	—	$	—	$	55,482	$	—
	Agency securities transferred to consolidated VIEs		—		1,221		—		—		1,266		—
	U.S. Treasury securities		4,328		—		—		2,427		—		—
	Interest rate swaps		—		70		—		—		136		—
	Swaptions		—		50		—		—		75		—
	REIT equity securities		68		—		—		68		—		—
	TBA securities		—		109		—		—		197		—
	Total		$	4,396	$	61,581	$	—	$	2,495	$	57,156	$	—
	Liabilities:
	Debt of consolidated VIEs		$	—	$	725	$	—	$	—	$	761	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements		3,363		—		—		5,363		—		—
	Interest rate swaps		—		1,308		—		—		880		—
	U.S. Treasury futures		14		—		—		5		—		—
	TBA securities		—		30		—		—		5		—
	Total		$	3,377	$	2,063	$	—	$	5,368	$	1,646	$	—
	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 the fair value of the agency MBS transferred to consolidated VIEs, less the fair value of our retained interests, which are based on valuations obtained from third-party pricing services and non-binding dealer quotes derived from common market pricing methods using "Level 2" inputs.
	Excluded from the table above are financial instruments, including cash and cash equivalents, restricted cash, receivables, payables and borrowings under repurchase agreements, which are presented in our consolidated financial statements at cost, which is determined to approximate fair value, primarily due to the short duration of these instruments. The cost basis of repo borrowings with initial terms of greater than one year is determined to approximate fair value, primarily as such agreements have floating rates based on an index plus or minus a fixed spread and the fixed spread is generally consistent with those demanded in the market.    We estimate the fair value of these instruments using "Level 2" inputs.

Stockholders_Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity
	Preferred Stock
	Pursuant to our amended and restated certificate of incorporation, we are authorized to designate and issue up to 10.0 million shares of preferred stock in one or more classes or series. Our Board of Directors has designated 6.9 million shares as 8.000% Series A Cumulative Redeemable Preferred Stock ("Series A Preferred Stock") and 8,050 shares as 7.750% Series B Cumulative Redeemable Preferred Stock ("Series B Preferred Stock"). As of March 31, 2015, we had 3.1 million shares of authorized but unissued shares of preferred stock. Our Board of Directors may designate additional series of authorized preferred stock ranking junior to or in parity with the Series A or Series B Preferred Stock or designate additional shares of the Series A or Series B Preferred Stock and authorize the issuance of such shares.
	In April 2012, we completed a public offering in which 6.9 million shares of our Series A Preferred Stock were sold to the underwriters at a price of $24.2125 per share for proceeds, net of offering expenses, of $167 million. In May 2014, we completed a public offering in which 7.0 million depositary shares were sold to the underwriters at a price of $24.2125 per depositary share for proceeds, net of offering expenses, of $169 million. Each depositary share represents a 1/1,000th interest in a share of our Series B Preferred Stock.
	Our Series A and Series B Preferred Stock have no stated maturity, are not subject to any sinking fund or mandatory redemption and rank on parity with each other. Under certain circumstances upon a change of control, our Series A and Series B Preferred Stock are convertible to shares of our common stock. Holders of our Series A Preferred Stock and depository shares underlying our Series B Preferred Stock have no voting rights, except under limited conditions, and are entitled to receive cumulative cash dividends at a rate of 8.000% and 7.750% per annum, respectively, of their $25.00 per share and $25.00 per depositary share liquidation preference, respectively, before holders of our common stock are entitled to receive any dividends. Shares of our Series A Preferred Stock and depository shares underlying our Series B Preferred Stock are each redeemable at $25.00 per share, plus accumulated and unpaid dividends (whether or not declared) exclusively at our option commencing on April 5, 2017 and May 8, 2019, respectively, or earlier under certain circumstances intended to preserve our qualification as a REIT for federal income tax purposes. Dividends are payable quarterly in arrears on the 15th day of each January, April, July and October. As of March 31, 2015, we had declared all required quarterly dividends on our Series A and Series B Preferred Stock.
	Common Stock Repurchase Program
	Our Board of Directors adopted a program that authorizes repurchases of our common stock through December 31, 2015, up to a specified amount. 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.  Among other factors, we intend to only consider repurchasing shares of our common stock when the purchase price is less than our estimate of our current net asset value per common share. 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.
	We did not repurchase any shares of our common stock during the three months ended March 31, 2015. 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, 2015, the total remaining amount authorized for repurchases of our common stock was $992 million.
	Accumulated Other Comprehensive Income (Loss)
	The following tables summarize changes to accumulated OCI for the three months ended March 31, 2015 and 2014 (in millions):
	Accumulated Other Comprehensive Income (Loss)	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated
								OCI
								Balance
	Three Months Ended March 31, 2015
	Balance as of December 31, 2014	$	570		$	(140	)	$	430
	OCI before reclassifications	427			—			427
	Amounts reclassified from accumulated OCI	(36		)	29			(7		)
	Balance as of March 31, 2015	$	961		$	(111	)	$	850
	Three Months Ended March 31, 2014
	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	)
	The following tables summarize reclassifications out of accumulated OCI for the three months ended March 31, 2015 and 2014 (in millions):
		Three Months Ended March 31,						Line Item in the Consolidated
								Statements of Comprehensive Income
	Amounts Reclassified from Accumulated OCI	2015			2014			Where Net Income is Presented
	(Gain) loss amounts reclassified from accumulated OCI for available-for-sale MBS	$	(36	)	$	19		Gain (loss) on sale of agency securities, net
	Periodic interest costs of interest rate swaps previously designated as hedges under GAAP, net	29			43			Interest expense
	Total reclassifications	$	(7	)	$	62

Subsequent_Event

Subsequent Event	3 Months Ended
	Mar. 31, 2015
Subsequent Events [Abstract]
Subsequent Event	Subsequent Events
	On April 13, 2015, our Board of Directors declared a monthly dividend of $0.22 per common share, which will be paid on May 8, 2015, to common stockholders of record as of April 30, 2015.
	On April 27, 2015, our Board of Directors declared a monthly dividend of $0.20 per common share, which will be paid on June 5, 2015, to common stockholders of record as of May 29, 2015.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
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 valuations obtained from third-party pricing services and non-binding dealer quotes derived from common market pricing methods using observable (or "Level 2") inputs. 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 based on a market approach using quoted market prices (or "Level 1" inputs). 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 exists 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.
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 effective 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. 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.
	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	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 in the "to-be-announced" market on a generic pool basis ("TBA securities") 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 may also 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 derivative instruments 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, with swap agreements entered into subsequent to May 2013 subject to central clearing 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" interest rate swaps based on valuations obtained from third-party pricing services and the swap counterparty (collectively, “third-party valuations”). The third-party valuations are model-driven using observable inputs consisting of LIBOR and the forward yield curve. We also consider the creditworthiness of both us and our counterparties and the impact of netting and credit enhancement provisions contained in each derivative agreement, such as collateral postings. All of our "non-centrally cleared" interest rate swaps are subject to bilateral collateral arrangements. Consequently, no credit valuation adjustment was made in determining the fair value of such instruments.
	Interest rate swaptions
	We purchase interest rate swaptions generally to help mitigate the potential impact of larger, more rapid changes in interest rates on the performance of our investment portfolio. 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 our interest rate swaption agreements based on model-driven valuations obtained from third-party pricing services and the swaption counterparty using observable inputs, taking into account 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_Tables

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2015
Investments, Debt and Equity Securities [Abstract]
Components of Investment Securities	The following tables summarize our investments in agency MBS as of March 31, 2015 and December 31, 2014 (dollars in millions):
			31-Mar-15
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	58,235		$	977			$	(72	)		$	59,140
	Adjustable rate		622			20				—				642
	CMO		1,138			35				—				1,173
	Interest-only and principal-only strips		354			46				(3		)		397
	Total agency MBS		$	60,349		$	1,078			$	(75	)		$	61,352
			December 31, 2014
	Agency MBS		Amortized			Gross				Gross				Fair Value
			Cost			Unrealized				Unrealized
						Gain				Loss
	Fixed rate		$	53,945		$	715			$	(187	)		$	54,473
	Adjustable rate		659			19				—				678
	CMO		1,172			24				(1		)		1,195
	Interest-only and principal-only strips		372			33				(3		)		402
	Total agency MBS		$	56,148		$	791			$	(191	)		$	56,748
Agency Securities
			December 31, 2014
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	42,749		$	10,566			$	107			$	53,422
	Unamortized discount		(37		)	(5		)		—				(42		)
	Unamortized premium		1,880			514				2				2,396
	Amortized cost		44,592			11,075				109				55,776
	Gross unrealized gains		610			145				3				758
	Gross unrealized losses		(127		)	(61		)		—				(188		)
	Total available-for-sale agency MBS, at fair value		45,075			11,159				112				56,346
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		348			24				—				372
	Gross unrealized gains		30			3				—				33
	Gross unrealized losses		(2		)	(1		)		—				(3		)
	Total agency MBS remeasured at fair value through earnings		376			26				—				402
	Total agency MBS, at fair value		$	45,451		$	11,185			$	112			$	56,748
	Weighted average coupon as of December 31, 2014 2		3.63		%	3.7		%		3.52		%		3.65		%
	Weighted average yield as of December 31, 2014 3		2.75		%	2.73		%		1.87		%		2.74		%
	Weighted average yield for the year ended December 31, 2014 3		2.62		%	2.64		%		1.66		%		2.63		%
	________________________
	1	The underlying UPB of our interest-only agency MBS strips was $1.2 billion and the weighted average contractual interest we are entitled to receive was 5.46% of this amount as of December 31, 2014. The par value of our principal-only agency MBS strips was $242 million as of December 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 December 31, 2014.
	3	Incorporates a weighted average future constant prepayment rate assumption of 9% based on forward rates as of December 31, 2014.
			31-Mar-15
	Agency MBS		Fannie Mae			Freddie Mac				Ginnie Mae				Total
	Available-for-sale agency MBS:
	Agency MBS, par		$	44,954		$	12,231			$	289			$	57,474
	Unamortized discount		(36		)	(5		)		—				(41		)
	Unamortized premium		1,944			606				12				2,562
	Amortized cost		46,862			12,832				301				59,995
	Gross unrealized gains		823			205				4				1,032
	Gross unrealized losses		(49		)	(23		)		—				(72		)
	Total available-for-sale agency MBS, at fair value		47,636			13,014				305				60,955
	Agency MBS remeasured at fair value through earnings:
	Interest-only and principal-only strips, amortized cost 1		331			23				—				354
	Gross unrealized gains		43			3				—				46
	Gross unrealized losses		(2		)	(1		)		—				(3		)
	Total agency MBS remeasured at fair value through earnings		372			25				—				397
	Total agency MBS, at fair value		$	48,008		$	13,039			$	305			$	61,352
	Weighted average coupon as of March 31, 2015 2		3.55		%	3.7		%		3.16		%		3.58		%
	Weighted average yield as of March 31, 2015 3		2.63		%	2.71		%		1.61		%		2.64		%
	Weighted average yield for the quarter ended March 31, 2015 3		2.56		%	2.58		%		1.63		%		2.57		%
	________________________
	1	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.1 billion and the weighted average contractual interest we are entitled to receive was 5.45% of this amount as of March 31, 2015. The par value of our principal-only agency MBS strips was $235 million as of March 31, 2015.
	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, 2015.
	3	Incorporates a weighted average future constant prepayment rate assumption of 10% based on forward rates as of March 31, 2015.
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, 2015 and December 31, 2014 according to their estimated weighted average life classification (dollars in millions):
			31-Mar-15											December 31, 2014
	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 and ≤ 3 years		1,049			1,032				3.36%		1.64%		289			280		4.08%		2.62%
	> 3 years and ≤ 5 years		23,885			23,373				3.27%		2.37%		22,153			21,820		3.26%		2.40%
	> 5 years and ≤10 years		35,898			35,471				3.64%		2.80%		33,271			33,055		3.73%		2.92%
	> 10 years		123			119				3.75%		3.28%		633			621		3.28%		3.15%
	Total		$	60,955		$	59,995			3.49%		2.61%		$	56,346		$	55,776	3.54%		2.72%
	_______________________
	1	Excludes interest and principal-only strips.
Summary of Changes in Accumulated OCI for Agency Securities	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, 2015 and 2014 (in millions):
	Agency Securities Classified as		Beginning Accumulated OCI			Unrealized			Reversal of			Ending
	Available-for-Sale		Balance			Gains and (Losses), Net			Unrealized			Accumulated
									(Gains) and Losses,			OCI
									Net on Realization			Balance
	Three months ended March 31, 2015		$	570		427			(36	)		$	961
	Three months ended March 31, 2014		$	(1,087	)	502			19			$	(566	)
Summary of Continuous Unrealized Loss Position of Available for Sale Securities	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, 2015 and December 31, 2014 (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, 2015		$	542		$	(3	)		$	7,942			$	(69	)	$	8,484	$	(72	)
	December 31, 2014		$	778		$	(2	)		$	11,679			$	(186	)	$	12,457	$	(188	)
Summary of Net Gain from Sale of Agency Securities	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, 2015 and 2014 (in millions):
			Three Months Ended March 31,
	Agency Securities Classified as		2015			2014
	Available-for-Sale
	Agency MBS sold, at cost		$	(7,732	)	$	(9,711	)
	Proceeds from agency MBS sold 1		7,768			9,692
	Net gain (loss) on sale of agency MBS		$	36		$	(19	)
	Gross gain on sale of agency MBS		$	57		$	42
	Gross loss on sale of agency MBS		(21		)	(61		)
	Net gain (loss) on sale of agency MBS		$	36		$	(19	)
	________________________
	1	Proceeds include cash received during the period, plus receivable for agency MBS sold during the period as of period end.

Recovered_Sheet1

Repurchase Agreements and Other Debt (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure of Repurchase Agreements [Abstract]
Schedule of Borrowings under Repurchase Agreements and Weighted Average Interest Rates	The following table summarizes our borrowings under repurchase arrangements and weighted average interest rates classified by remaining maturities as of March 31, 2015 and December 31, 2014 (dollars in millions):
		31-Mar-15					December 31, 2014
	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	$	24,680	0.36	%	16	$	14,157	0.37	%	15
	> 1 to ≤ 3 months	15,100		0.38	%	52	20,223		0.38	%	61
	> 3 to ≤ 6 months	5,455		0.43	%	132	6,654		0.42	%	120
	> 6 to ≤ 9 months	2,668		0.56	%	222	1,575		0.5	%	225
	> 9 to ≤ 12 months	1,826		0.47	%	330	2,678		0.54	%	313
	> 12 to ≤ 24 months	700		0.61	%	491	600		0.57	%	551
	> 24 to ≤ 36 months	852		0.61	%	937	952		0.6	%	999
	> 36 to ≤ 48 months	1,150		0.68	%	1,268	650		0.64	%	1,266
	> 48 to < 60 months	1,900		0.7	%	1,706	900		0.68	%	1,542
	Total agency MBS	54,331		0.41	%	164	48,389		0.41	%	143
	U.S. Treasury securities:
	1 day	3,781		0.21	%	1	1,907		0.09	%	1
	Total / Weighted Average	$	58,112	0.33	%	142	$	50,296	0.4	%	138

Derivative_and_Other_Hedging_I1

Derivative and Other Hedging Instruments (Tables)	3 Months Ended
	Mar. 31, 2015
Derivative [Line Items]
Schedule of Outstanding Derivatives Not Designated as Hedging Instruments	The table below summarizes fair value information about our derivative and other hedging instrument assets and liabilities as of March 31, 2015 and December 31, 2014 (in millions):
	Derivative and Other Hedging Instruments		Balance Sheet Location		March 31, 2015				December 31, 2014
	Interest rate swaps		Derivative assets, at fair value		$	70			$	136
	Swaptions		Derivative assets, at fair value		50				75
	TBA securities		Derivative assets, at fair value		109				197
	Total				$	229			$	408
	Interest rate swaps		Derivative liabilities, at fair value		$	(1,308	)		$	(880	)
	TBA securities		Derivative liabilities, at fair value		(30		)		(5		)
	U.S. Treasury futures - short		Derivative liabilities, at fair value		(14		)		(5		)
	Total				$	(1,352	)		$	(890	)
	U.S. Treasury securities - long		U.S. Treasury securities, at fair value		$	4,328			$	2,427
	U.S. Treasury securities - short		Obligation to return securities borrowed under reverse repurchase agreements, at fair value 1		(3,363		)		(5,363		)
	Total - (short)/long, net				$	965			$	(2,936	)
	________________________
	1	Our obligation to return securities borrowed under reverse repurchase agreements as of March 31, 2015 and December 31, 2014 relates to securities borrowed to cover short sales of U.S. Treasury securities from which we received total sale proceeds of $3.3 billion and $5.4 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.
Schedule of Interest Rate Swaption Agreements Outstanding	The following table summarizes our interest rate payer swaption agreements outstanding as of March 31, 2015 and December 31, 2014 (dollars in millions):
	Payer Swaptions		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)
	31-Mar-15
	≤ 1 year		$	117			$	28			7		$	4,650			3.33%		3M		7.1
	> 1 to ≤ 2 years		13				1				16		550				4.01%		3M		5.7
	Total Payer Swaptions		$	130			$	29			8		$	5,200			3.40%		3M		7
	31-Dec-14
	≤ 1 year		$	113			$	36			6		$	5,600			3.15%		3M		6.4
	> 1 to ≤ 2 years		32				10				16		1,200				3.87%		3M		5.1
	Total Payer Swaptions		$	145			$	46			8		$	6,800			3.28%		3M		6.2
	The following table summarizes our interest rate receiver swaption agreements outstanding as of March 31, 2015 and December 31, 2014 (dollars in millions):
	Receiver Swaptions		Option										Underlying Receiver Swap
	Years to Expiration		Cost				Fair				Average		Notional				Average Fixed Receive		Average		Average
							Value				Months to		Amount				Rate		Pay		Term
											Expiration								Rate		(Years)
																			(LIBOR)
	31-Mar-15
	≤ 1 year		$	6			$	21			2		$	750			1.96%		3M		6.7
	31-Dec-14
	≤ 1 year		$	18			$	29			5		$	4,250			1.78%		3M		6.4
US government securities	The following table summarizes our U.S. Treasury securities as of March 31, 2015 and December 31, 2014 (in millions):
			31-Mar-15												31-Dec-14
	Maturity		Face Amount Net Long / (Short)				Cost Basis				Market Value				Face Amount Net Long / (Short)				Cost Basis			Market Value
	3 years		$	(900	)		$	(899	)		$	(902	)		$	—			$	—		$	—
	5 years		(2,111		)		(2,096		)		(2,116		)		(4,674		)		(4,650		)	(4,645		)
	7 years		(339		)		(334		)		(341		)		(717		)		(717		)	(718		)
	10 years		4,258				4,303				4,324				2,410				2,422			2,427
	Total U.S. Treasury securities, net		$	908			$	974			$	965			$	(2,981	)		$	(2,945	)	$	(2,936	)
Summary of Long and Short Position of Derivative Instruments	The following tables summarize our TBA securities as of March 31, 2015 and December 31, 2014 (in millions):
			31-Mar-15																31-Dec-14
	TBA Securities by Coupon		Notional				Cost				Market				Net Carrying Value 4				Notional			Cost			Market			Net Carrying Value 4
			Amount - Long (Short) 1				Basis 2				Value 3								Amount - Long (Short) 1			Basis 2			Value 3
	15-Year TBA securities:
	2.50%		$	1,632			$	1,670			$	1,673			$	3			$	962		$	968		$	980		$	12
	3.00%		(2,733		)		(2,852		)		(2,866		)		(14		)		2,779			2,889			2,888			(1		)
	3.50%		(192		)		(201		)		(203		)		(2		)		(468		)	(495		)	(494		)	1
	4.00%		—				—				—				—				(13		)	(14		)	(14		)	—
	Total 15-Year TBAs		(1,293		)		(1,383		)		(1,396		)		(13		)		3,260			3,348			3,360			12
	30-Year TBA securities:
	3.00%		5,432				5,500				5,566				66				5,254			5,259			5,313			54
	3.50%		3,423				3,560				3,598				38				7,902			8,151			8,232			81
	4.00%		(2,689		)		(2,862		)		(2,874		)		(12		)		(1,853		)	(2,019		)	(1,974		)	45
	4.50%		—				—				—				—				(151		)	(163		)	(163		)	—
	Total 30-Year TBAs		6,166				6,198				6,290				92				11,152			11,228			11,408			180
	Total net TBA securities		$	4,873			$	4,815			$	4,894			$	79			$	14,412		$	14,576		$	14,768		$	192
			31-Mar-15																31-Dec-14
	TBA Securities by Issuer		Notional				Cost				Market				Net Carrying Value 4				Notional			Cost			Market			Net Carrying Value 4
			Amount - Long (Short) 1				Basis 2				Value 3								Amount - Long (Short) 1			Basis 2			Value 3
	Fannie Mae		$	2,230			$	2,125			$	2,178			$	53			$	15,127		$	15,316		$	15,509		$	193
	Freddie Mac		(957		)		(1,021		)		(1,025		)		(4		)		(715		)	(740		)	(741		)	(1		)
	Ginnie Mae		3,600				3,711				3,741				30				—			—			—			—
	TBA securities, net		$	4,873			$	4,815			$	4,894			$	79			$	14,412		$	14,576		$	14,768		$	192
	_____________________
	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.
Schedule Of Outstanding Not Designated As Hedging Instruments	The tables below summarize changes in our derivative and other hedge portfolio and their effect on our consolidated statements of comprehensive income for the three months ended March 31, 2015 and 2014 (in millions):
			Three Months Ended March 31, 2015
	Derivative and Other Hedging Instruments		Notional Amount				Additions			Settlement, Termination,			Notional Amount					Amount of
			Long/(Short)							Expiration or			Long/(Short) March 31, 2015					Gain/(Loss)
			31-Dec-14							Exercise								Recognized in
																		Income on
																		Derivatives 1
	TBA securities, net		$	14,412			45,500			(55,039	)		$	4,873				$	234
	Interest rate swaps		$	(43,700	)		(3,500	)		2,275			$	(44,925	)			(746		)
	Payer swaptions		$	(6,800	)		—			1,600			$	(5,200	)			(17		)
	Receiver swaptions		$	4,250			—			(3,500	)		$	750				17
	U.S. Treasury securities - short position		$	(5,392	)		(4,173	)		6,212			$	(3,353	)			(82		)
	U.S. Treasury securities - long position		$	2,411			15,562			(13,712	)		$	4,261				52
	U.S. Treasury futures contracts - short position		$	(730	)		(730	)		730			$	(730	)			(20		)
																		$	(562	)
	________________________________
	1	Excludes a net gain of $2 million from investments in REIT equity securities and a net gain of $11 million from interest and principal-only securities recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income.
			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
	TBA securities, net		$	2,119			24,376			(12,586	)		$	13,909				$	60
	Interest rate swaps		$	(43,250	)		(5,900	)		2,750			$	(46,400	)			(380		)
	Payer swaptions		$	(14,250	)		(1,000	)		7,250			$	(8,000	)			(105		)
	Receiver swaptions		$	—			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 from 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.
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, 2015 and December 31, 2014 (dollars in millions):
			31-Mar-15
	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		$	14,850			1.21%		0.24%		$	(110	)		1.9
	> 3 to ≤ 5 years		10,475				1.74%		0.26%		(149		)		4.3
	> 5 to ≤ 7 years		7,050				2.61%		0.26%		(309		)		6.2
	> 7 to ≤ 10 years		9,825				2.45%		0.26%		(405		)		8.2
	> 10 years		2,725				3.15%		0.26%		(265		)		12.5
	Total Payer Interest Rate Swaps		$	44,925			1.94%		0.25%		$	(1,238	)		5.2
	________________________
	1	Notional amount includes forward starting swaps of $10.1 billion with an average forward start date of 0.9 years and an average maturity of 7.3 years from March 31, 2015.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.64% as of March 31, 2015.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from March 31, 2015 through stated maturity date.
			December 31, 2014
	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		$	12,300			1.33%		0.21%		$	(87	)		2
	> 3 to ≤ 5 years		8,975				1.63%		0.24%		(4		)		4.2
	> 5 to ≤ 7 years		7,250				2.47%		0.23%		(139		)		6.1
	> 7 to ≤ 10 years		10,775				2.48%		0.24%		(223		)		8.3
	> 10 years		4,400				3.19%		0.23%		(291		)		12.6
	Total Payer Interest Rate Swaps		$	43,700			2.05%		0.23%		$	(744	)		5.8
	________________________
	1	Notional amount includes forward starting swaps of $12.4 billion with an average forward start date of 1.1 years and an average maturity of 7.9 years from December 31, 2014.
	2	Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.68% as of December 31, 2014.
	3	Average receive rate excludes forward starting swaps.
	4	Average maturity measured from December 31, 2014 through stated maturity date.

Pledged_Assets_Tables

Pledged Assets (Tables)	3 Months Ended
	Mar. 31, 2015
Pledged Assets [Abstract]
Schedule of Financial Instruments Owned and Pledged as Collateral	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, 2015 and December 31, 2014 (in millions):
			March 31, 2015
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	57,245	$	1,221	$	171	$	141		$	58,778
	U.S. Treasury securities - fair value		3,789		—		539		—			4,328
	Accrued interest on pledged securities		176		4		2		—			182
	Restricted cash		29		—		1,077		2			1,108
	Total		$	61,239	$	1,225	$	1,789	$	143		$	64,396
			December 31, 2014
	Assets Pledged to Counterparties		Repurchase Agreements		Debt of Consolidated VIEs		Derivative Agreements		Prime Broker Agreements			Total
	Agency MBS - fair value		$	50,858	$	1,266	$	69	$	702		$	52,895
	U.S. Treasury securities - fair value		1,904		—		550		—			2,454
	Accrued interest on pledged securities		147		4		2		—			153
	Restricted cash		6		—		698		9			713
	Total		$	52,915	$	1,270	$	1,319	$	711		$	56,215
Schedules Of Securities Pledged As Collateral Under Repurchase Agreement	The following table summarizes our securities pledged as collateral under repurchase agreements and other debt of consolidated VIEs by remaining maturity of the repurchase agreement and other debt liability, including securities pledged related to sold but not yet settled securities, as of March 31, 2015 and December 31, 2014 (in millions). For the corresponding repurchase agreement and other debt liability associated with the following amounts and the interest rates thereon, refer to Note 5.
			March 31, 2015						December 31, 2014
	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		$	25,572	$	25,188	$	69	$	14,605		$	14,453		$	41
	> 30 and ≤ 60 days		11,932		11,731		32		10,912			10,789			30
	> 60 and ≤ 90 days		3,937		3,880		11		10,205			10,109			28
	> 90 days		17,025		16,728		47		16,402			16,227			47
	Total agency MBS		58,466		57,527		159		52,124			51,578			146
	U.S. Treasury securities:
	1 day		3,789		3,774		21		1,904			1,899			5
	Total		$	62,255	$	61,301	$	180	$	54,028		$	53,477		$	151
Schedule of Securities and Cash Pledged as Collateral from Counterparties	As of March 31, 2015 and December 31, 2014, we had assets pledged to us from counterparties as collateral under our reverse repurchase and derivative agreements summarized in the tables below (in millions).
			March 31, 2015						December 31, 2014
	Assets Pledged to AGNC		Reverse Repurchase Agreements		Derivative Agreements		Total		Reverse Repurchase Agreements			Derivative Agreements			Total
	Agency MBS - fair value		$	—	$	14	$	14	$	—		$	43		$	43
	U.S. Treasury securities - fair value		3,363		—		3,363		5,363			47			5,410
	Cash		—		—		—		—			28			28
	Total		$	3,363	$	14	$	3,377	$	5,363		$	118		$	5,481
Offsetting Assets and Liabilities	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, 2015 and December 31, 2014 (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-15
	Interest rate swap and swaption agreements, at fair value 1		$	120	$	—	$	120	$	(97	)	$	(14	)	$	9
	Receivable under reverse repurchase agreements		3,175		—		3,175		(3,175		)	—			—
	Total derivative, other hedging instruments and other assets		$	3,295	$	—	$	3,295	$	(3,272	)	$	(14	)	$	9
	31-Dec-14
	Interest rate swap and swaption agreements, at fair value 1		$	211	$	—	$	211	$	(94	)	$	(83	)	$	34
	Receivable under reverse repurchase agreements		5,218		—		5,218		(4,690		)	(528		)	—
	Total derivative, other hedging instruments and other assets		$	5,429	$	—	$	5,429	$	(4,784	)	$	(611	)	$	34
Offsetting Liabilities
			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-15
	Interest rate swap agreements, at fair value 1		$	1,308	$	—	$	1,308	$	(97	)	$	(1,208	)	$	3
	Repurchase agreements		58,112		—		58,112		(3,175		)	(54,937		)	—
	Total derivative, other hedging instruments and other liabilities		$	59,420	$	—	$	59,420	$	(3,272	)	$	(56,145	)	$	3
	31-Dec-14
	Interest rate swap agreements, at fair value 1		$	880	$	—	$	880	$	(94	)	$	(782	)	$	4
	Repurchase agreements		50,296		—		50,296		(4,690		)	(45,606		)	—
	Total derivative, other hedging instruments and other liabilities		$	51,176	$	—	$	51,176	$	(4,784	)	$	(46,388	)	$	4
	_______________________
	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.

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2015
Fair Value Disclosures [Abstract]
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, 2015 and December 31, 2014 (in millions):
		March 31, 2015						December 31, 2014
		Level 1		Level 2		Level 3		Level 1		Level 2		Level 3
	Assets:
	Agency securities	$	—	$	60,131	$	—	$	—	$	55,482	$	—
	Agency securities transferred to consolidated VIEs	—		1,221		—		—		1,266		—
	U.S. Treasury securities	4,328		—		—		2,427		—		—
	Interest rate swaps	—		70		—		—		136		—
	Swaptions	—		50		—		—		75		—
	REIT equity securities	68		—		—		68		—		—
	TBA securities	—		109		—		—		197		—
	Total	$	4,396	$	61,581	$	—	$	2,495	$	57,156	$	—
	Liabilities:
	Debt of consolidated VIEs	$	—	$	725	$	—	$	—	$	761	$	—
	Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements	3,363		—		—		5,363		—		—
	Interest rate swaps	—		1,308		—		—		880		—
	U.S. Treasury futures	14		—		—		5		—		—
	TBA securities	—		30		—		—		5		—
	Total	$	3,377	$	2,063	$	—	$	5,368	$	1,646	$	—

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following tables summarize changes to accumulated OCI for the three months ended March 31, 2015 and 2014 (in millions):
	Accumulated Other Comprehensive Income (Loss)	Net Unrealized Gain (Loss) on Available-for-Sale MBS			Net Unrealized Gain (Loss) on Swaps			Total Accumulated
								OCI
								Balance
	Three Months Ended March 31, 2015
	Balance as of December 31, 2014	$	570		$	(140	)	$	430
	OCI before reclassifications	427			—			427
	Amounts reclassified from accumulated OCI	(36		)	29			(7		)
	Balance as of March 31, 2015	$	961		$	(111	)	$	850
	Three Months Ended March 31, 2014
	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	)
	The following tables summarize reclassifications out of accumulated OCI for the three months ended March 31, 2015 and 2014 (in millions):
		Three Months Ended March 31,						Line Item in the Consolidated
								Statements of Comprehensive Income
	Amounts Reclassified from Accumulated OCI	2015			2014			Where Net Income is Presented
	(Gain) loss amounts reclassified from accumulated OCI for available-for-sale MBS	$	(36	)	$	19		Gain (loss) on sale of agency securities, net
	Periodic interest costs of interest rate swaps previously designated as hedges under GAAP, net	29			43			Interest expense
	Total reclassifications	$	(7	)	$	62

Organization_Details

Organization (Details)	3 Months Ended
	Mar. 31, 2015
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Required distribution of taxable net income on a annual basis	90.00%
Intended annual distribution of taxable net income	100.00%

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (Maximum [Member], Interest Rate Swap [Member])	3 Months Ended
	Mar. 31, 2015
Maximum [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Term of derivative contract	20 years

Investment_Securities_Narrativ

Investment Securities (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Total agency MBS, at fair value	$61,352,000,000		$56,748,000,000
Weighted average expected constant prepayment rate	10.00%		9.00%
Weighted average life of interest-only strips	5 years 8 months 10 days		6 years 17 days
Weighted average life of principal-only strips	7 years 6 months 19 days		8 years 28 days
Agency securities, total fair value	1,200,000,000		1,300,000,000
Debt, at fair value	725,000,000		761,000,000
Principal balance of agency securities collaterizing debt issued by securitization trust	-1,100,000,000		1,200,000,000
Principal amount	707,000,000		742,000,000
Gain (loss) associated with consolidated debt	0	-3,000,000
Fair value of CMO securities and interest-only and principal-only strips	1,600,000,000
Securitized CMO Securities	2,100,000,000
CMO and Interest Only, Principal Only Securities, Maximum Loss Exposure	289,000,000		274,000,000
Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unamortized premium balance	2,600,000,000		2,500,000,000
Interest Only And Principal Only Strip [Member]
Schedule of Available-for-sale Securities [Line Items]
Net unrealized gain	11,000,000	12,000,000
TBA securities Fifteen Year and Thirty Year Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Net long TBA position, at fair value	4,900,000,000		14,800,000,000
TBA, net carrying value	$79,000,000		$192,000,000

Investment_Securities_Summary_

Investment Securities (Summary of Investment in Agency Security) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Amortized cost	$59,995	$55,776
Gross unrealized gain	1,078	791
Gross unrealized loss	-75	-191
Fair value	60,955	56,346
Total agency MBS, amortized cost	60,349	56,148
Total agency MBS, at fair value	61,352	56,748
Fixed Income Securities [Member]
Gross unrealized gain	977	715
Gross unrealized loss	-72	-187
Fixed Income Securities [Member] | Agency Securities [Member]
Amortized cost	58,235	53,945
Fair value	59,140	54,473
Adjustable-Rate [Member]
Gross unrealized gain	20	19
Gross unrealized loss	0	0
Adjustable-Rate [Member] | Agency Securities [Member]
Amortized cost	622	659
Fair value	642	678
Collateralized Mortgage Obligations [Member]
Gross unrealized gain	35	24
Gross unrealized loss	0	-1
Collateralized Mortgage Obligations [Member] | Agency Securities [Member]
Amortized cost	1,138	1,172
Fair value	1,173	1,195
Interest Only And Principal Only Strip [Member]
Gross unrealized gain	46	33
Gross unrealized loss	-3	-3
Interest Only And Principal Only Strip [Member] | Agency Securities [Member]
Interest-only and principal-only strips, amortized cost	354	372
Interest-only and principal-only strips, fair value	$397	$402

Investment_Securities_Componen

Investment Securities (Components Of Investment Securities) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Schedule of Investments [Line Items]
Amortized cost	$59,995,000,000		$55,776,000,000
Total agency MBS, at fair value	61,352,000,000		56,748,000,000
Weighted average coupon	3.58%		3.65%	[1]
Weighted average yield	2.64%		2.74%	[2]
Weighted average yield for the year ended	2.57%		2.63%
Unamortized Principal Balance Of Interest Only Strips	1,100,000,000		1,200,000,000
Weighted Average Contractual Interest Rate Of Interest Only Strips	5.45%		5.46%
Unamortized Principal Balance Of Principal Only Strips	235,000,000		242,000,000
Future Prepayment Rate Assumption Of Investment Portfolio	10.00%		9.00%
Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Agency MBS, par	57,474,000,000		53,422,000,000
Unamortized discount	-41,000,000		-42,000,000
Unamortized premium	2,562,000,000		2,396,000,000
Amortized cost	59,995,000,000		55,776,000,000
Gross unrealized gains	1,032,000,000		758,000,000
Gross unrealized losses	-72,000,000		-188,000,000
Total available-for-sale agency MBS, at fair value	60,955,000,000		56,346,000,000
Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Interest-only and principal-only strips, amortized cost	354,000,000		372,000,000
Gross unrealized gains	46,000,000		33,000,000
Gross unrealized losses	-3,000,000		-3,000,000
Total agency MBS remeasured at fair value through earnings	397,000,000		402,000,000
Fannie Mae [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	48,008,000,000		45,451,000,000
Weighted average coupon	3.55%	[1]	3.63%	[1]
Weighted average yield	2.63%	[2]	2.75%	[2]
Weighted average yield for the year ended	2.56%		2.62%
Fannie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Agency MBS, par	44,954,000,000		42,749,000,000
Unamortized discount	-36,000,000		-37,000,000
Unamortized premium	1,944,000,000		1,880,000,000
Amortized cost	46,862,000,000		44,592,000,000
Gross unrealized gains	823,000,000		610,000,000
Gross unrealized losses	-49,000,000		-127,000,000
Total available-for-sale agency MBS, at fair value	47,636,000,000		45,075,000,000
Fannie Mae [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Interest-only and principal-only strips, amortized cost	331,000,000		348,000,000
Gross unrealized gains	43,000,000		30,000,000
Gross unrealized losses	-2,000,000		-2,000,000
Total agency MBS remeasured at fair value through earnings	372,000,000		376,000,000
Freddie Mac [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	13,039,000,000		11,185,000,000
Weighted average coupon	3.70%	[1]	3.70%	[1]
Weighted average yield	2.71%	[2]	2.73%	[2]
Weighted average yield for the year ended	2.58%		2.64%
Freddie Mac [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Agency MBS, par	12,231,000,000		10,566,000,000
Unamortized discount	-5,000,000		-5,000,000
Unamortized premium	606,000,000		514,000,000
Amortized cost	12,832,000,000		11,075,000,000
Gross unrealized gains	205,000,000		145,000,000
Gross unrealized losses	-23,000,000		-61,000,000
Total available-for-sale agency MBS, at fair value	13,014,000,000		11,159,000,000
Freddie Mac [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Interest-only and principal-only strips, amortized cost	23,000,000		24,000,000
Gross unrealized gains	3,000,000		3,000,000
Gross unrealized losses	-1,000,000		-1,000,000
Total agency MBS remeasured at fair value through earnings	25,000,000		26,000,000
Ginnie Mae [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	305,000,000		112,000,000
Weighted average coupon	3.16%	[1]	3.52%	[1]
Weighted average yield	1.61%	[2]	1.87%	[2]
Weighted average yield for the year ended	1.63%		1.66%
Ginnie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Agency MBS, par	289,000,000		107,000,000
Unamortized discount	0		0
Unamortized premium	12,000,000		2,000,000
Amortized cost	301,000,000		109,000,000
Gross unrealized gains	4,000,000		3,000,000
Gross unrealized losses	0		0
Total available-for-sale agency MBS, at fair value	305,000,000		112,000,000
Ginnie Mae [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
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	$0		$0
[1]	The underlying unamortized principal balance ("UPB" or "par value") of our interest-only agency MBS strips was $1.1 billion and the weighted average contractual interest we are entitled to receive was 5.45% of this amount as of MarchB 31, 2015. The par value of our principal-only agency MBS strips was $235 million as of MarchB 31, 2015.
[2]	Incorporates a weighted average future constant prepayment rate assumption of 10% based on forward rates as of MarchB 31, 2015

Investment_Securities_Summary_1

Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Agency securities classified as available for sale, Fair value	$60,955	$56,346
Agency securities classified as available for sale, Amortized cost	59,995	55,776
Weighted Average Coupon	3.49%	3.54%
Weighted Average Yield	2.61%	2.72%
Greater Than One Year and Less Than or Equal to Three Years [Member]
Fair Value	1,049	289
Amortized Cost	1,032	280
Weighted Average Coupon	3.36%	4.08%
Weighted Average Yield	1.64%	2.62%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Fair Value	23,885	22,153
Amortized Cost	23,373	21,820
Weighted Average Coupon	3.27%	3.26%
Weighted Average Yield	2.37%	2.40%
Greater Than Five Years [Member]
Fair Value	35,898	33,271
Amortized Cost	35,471	33,055
Weighted Average Coupon	3.64%	3.73%
Weighted Average Yield	2.80%	2.92%
Greater Than Ten Years [Member]
Fair Value	123	633
Amortized Cost	$119	$621
Weighted Average Coupon	3.75%	3.28%
Weighted Average Yield	3.28%	3.15%

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, 2015	Mar. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized Gains and (Losses), Net	$391	$521
Agency Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning OCI Balance	570	-1,087
Unrealized Gains and (Losses), Net	427	502
Reversal of Unrealized (Gains) and Losses, Net on Realization	-36	19
Ending OCI Balance	$961	($566)

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, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Member]
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$542	$778
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	-3	-2
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	7,942	11,679
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	-69	-186
Unrealized Loss Position For - Estimated Fair Value - Total	8,484	12,457
Unrealized Loss Position For - Unrealized Loss - Total	($72)	($188)

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, 2015	Mar. 31, 2014
Proceeds from agency MBS sold	$17,999	$12,807
Net gain (loss) on sale of agency MBS	36	-19
Agency Securities [Member]
Agency MBS sold, at cost	-7,732	-9,711
Proceeds from agency MBS sold	7,768	9,692
Net gain (loss) on sale of agency MBS	36	-19
Gross gain on sale of agency MBS	57	42
Gross loss on sale of agency MBS	($21)	($61)

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, 2015	Dec. 31, 2014
Disclosure of Repurchase Agreements [Abstract]
Debt of consolidated variable interest entities, at fair value	$725	$761
Description of variable rate basis	LIBOR
Basis spread over LIBOR	43
Principal amount	$707	$742
Weighted average life of other debt	5 years 6 months 30 days	5 years 9 months

Repurchase_Agreements_And_Othe2

Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Repurchase Agreements	$58,112	$50,296
Weighted Average Days to Maturity	142	138
30 Days or Less [Member]
Repurchase Agreements	24,680	14,157
Weighted Average Interest Rate	0.36%	0.37%
Weighted Average Days to Maturity	16	15
1 to 3 Months
Repurchase Agreements	15,100	20,223
Weighted Average Interest Rate	0.38%	0.38%
Weighted Average Days to Maturity	52	61
3 to 6 Months
Repurchase Agreements	5,455	6,654
Weighted Average Interest Rate	0.43%	0.42%
Weighted Average Days to Maturity	132	120
6 to 9 Months
Repurchase Agreements	2,668	1,575
Weighted Average Interest Rate	0.56%	0.50%
Weighted Average Days to Maturity	222	225
9 to 12 Months
Repurchase Agreements	1,826	2,678
Weighted Average Interest Rate	0.47%	0.54%
Weighted Average Days to Maturity	330	313
12 to 24 Months
Repurchase Agreements	700	600
Weighted Average Interest Rate	0.61%	0.57%
Weighted Average Days to Maturity	491	551
24 to 36 Months
Repurchase Agreements	852	952
Weighted Average Interest Rate	0.61%	0.60%
Weighted Average Days to Maturity	937	999
36 to 48 months
Repurchase Agreements	1,150	650
Weighted Average Interest Rate	0.68%	0.64%
Weighted Average Days to Maturity	1,268	1,266
48 to 60 Months
Repurchase Agreements	1,900	900
Weighted Average Interest Rate	0.70%	0.68%
Weighted Average Days to Maturity	1,706	1,542
Repurchase Agreements [Member]
Weighted Average Interest Rate	0.33%	0.40%
Agency Securities [Member]
Repurchase Agreements	54,331	48,389
Weighted Average Days to Maturity	164	143
Agency Securities [Member] | Repurchase Agreements [Member]
Weighted Average Interest Rate	0.41%	0.41%
US Treasury Securities [Member]
Repurchase Agreements	$3,781	$1,907
Weighted Average Interest Rate	0.21%	0.09%
Weighted Average Days to Maturity	1	1

Derivative_and_Other_Hedging_I2

Derivative and Other Hedging Instruments (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Unrealized gain on derivative instruments, net	$29	$43
Net periodic interest costs on swaps	113	126
Derivative Instruments, Gain Reclassified from Accumulated OCI into Income, Effective Portion	84	83
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net, De-Designated Interest Rate Swaps	-29	-43
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Deferred loss in accumulated OCI related to de-designated interest rate swaps	111	-253	140	296
Deferred loss expected to be reclassified from OCI into interest expense over the next twelve months	91
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member] | Interest Rate Swaps [Member]
Average Maturity (Years)	1 year 2 months 10 days
Interest Only And Principal Only Strip [Member]
Unrealized Gain (Loss) on Securities	$11	$12
Forward Contracts [Member] | Interest Rate Swap [Member]
Average Maturity (Years)	7 years 3 months 3 days		7 years 11 months 3 days

Derivative_and_Other_Hedging_I3

Derivative and Other Hedging Instruments (Fair Value Information) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Derivative asset, fair value	$229,000,000	$408,000,000
Derivative liability, fair value	-1,352,000,000	-890,000,000
Derivative assets, at fair value	229,000,000	408,000,000
U.S. Treasury securities	4,328,000,000	2,427,000,000
U.S. Treasury Securities - short	-3,363,000,000	-5,363,000,000
Total - (short)/long, net	965,000,000	-2,936,000,000
Proceeds from Securities Purchased under Agreements to Resell	3,300,000,000	5,400,000,000
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative liability, fair value	-1,308,000,000	-880,000,000
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	70,000,000	136,000,000
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	50,000,000	75,000,000
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative asset, fair value		197,000,000
Derivative liability, fair value	-30,000,000	-5,000,000
Future [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative liability, fair value	-14,000,000	-5,000,000
TBA and Forward Settling Agency Securities [Member] | Fair Value, Measurements, Recurring [Member] | Purchases Of TBAs And Forward Settling Agency Securities [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative assets, at fair value	$109,000,000	$197,000,000

Derivative_and_Other_Hedging_I4

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, 2015	Dec. 31, 2014
Interest Rate Swap [Member]
Notional Amount	$44,925	$43,700
Average Fixed Pay Rate	1.94%	2.05%
Average Receive Rate	0.25%	0.23%
Net Estimated Fair Value	-1,238	-744
Average Maturity (Years)	5 years 1 month 29 days	5 years 9 months 1 day
Forward Contracts [Member] | Interest Rate Swap [Member]
Average Maturity (Years)	7 years 3 months 3 days	7 years 11 months 3 days
Derivative, Notional Amount	10,100	12,400
Derivative, Higher Remaining Maturity Range	11 months 2 days	1 year 20 days
Interest Rate Swaps Excluding Forward Starting [Member] | Interest Rate Swap [Member]
Average Fixed Pay Rate	1.64%	1.68%
Greater Than One Year and Less Than or Equal to Three Years [Member] | Interest Rate Swap [Member]
Notional Amount	14,850	12,300
Average Fixed Pay Rate	1.21%	1.33%
Average Receive Rate	0.24%	0.21%
Net Estimated Fair Value	-110	-87
Average Maturity (Years)	1 year 11 months 9 days	2 years 6 days
Greater Than Three Years and Less Than or Equal to Five Years [Member] | Interest Rate Swap [Member]
Notional Amount	10,475	8,975
Average Fixed Pay Rate	1.74%	1.63%
Average Receive Rate	0.26%	0.24%
Net Estimated Fair Value	-149	-4
Average Maturity (Years)	4 years 3 months 11 days	4 years 2 months 7 days
Greater Than Five Years and Less than or Equal to Seven Years [Member] | Interest Rate Swap [Member]
Notional Amount	7,050	7,250
Average Fixed Pay Rate	2.61%	2.47%
Average Receive Rate	0.26%	0.23%
Net Estimated Fair Value	-309	-139
Average Maturity (Years)	6 years 1 month 30 days	6 years 24 days
Greater Than Seven Years and Less than or Equal to Ten Years [Member] | Interest Rate Swap [Member]
Notional Amount	9,825	10,775
Average Fixed Pay Rate	2.45%	2.48%
Average Receive Rate	0.26%	0.24%
Net Estimated Fair Value	-405	-223
Average Maturity (Years)	8 years 2 months 16 days	8 years 3 months 19 days
Greater Than Ten Years [Member] | Interest Rate Swap [Member]
Notional Amount	2,725	4,400
Average Fixed Pay Rate	3.15%	3.19%
Average Receive Rate	0.26%	0.23%
Net Estimated Fair Value	($265)	($291)
Average Maturity (Years)	12 years 6 months 14 days	12 years 7 months 14 days

Derivative_and_Other_Hedging_I5

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, 2015	Dec. 31, 2014
	month	month
Interest Rate Swaption [Member]
Cost	$130	$145
Fair Value	29	46
Average Months to Expiration	8	8
Notional Amount	5,200	6,800
Average Fixed Pay Rate	3.40%	3.28%
Average Maturity (Years)	7 years	6 years 1 month 29 days
Payer Swaption [Member]
Average Receive Rate (LIBOR)	3M	3M
Less Than or Equal to One Year [Member] | Interest Rate Swaption [Member]
Cost	117	113
Fair Value	28	36
Average Months to Expiration	7	6
Notional Amount	4,650	5,600
Average Fixed Pay Rate	3.33%	3.15%
Average Maturity (Years)	7 years 1 month	6 years 4 months 22 days
Less Than or Equal to One Year [Member] | Receiver Swaption [Member]
Cost	6	18
Fair Value	21	29
Average Months to Expiration	2	5
Notional Amount	750	4,250
Average Fixed Pay Rate	1.96%	1.78%
Average Receive Rate (LIBOR)	3M	3M
Average Maturity (Years)	6 years 8 months	6 years 4 months 7 days
Less Than or Equal to One Year [Member] | Payer Swaption [Member]
Average Receive Rate (LIBOR)	3M	3M
Greater Than One Year and Less Than or Equal to Three Years [Member] | Interest Rate Swaption [Member]
Cost	13	32
Fair Value	1	10
Average Months to Expiration	16	16
Notional Amount	$550	$1,200
Average Fixed Pay Rate	4.01%	3.87%
Average Maturity (Years)	5 years 8 months	5 years 30 days
Greater Than One Year and Less Than or Equal to Three Years [Member] | Payer Swaption [Member]
Average Receive Rate (LIBOR)	3M	3M

Derivative_and_Other_Hedging_I6

Derivative and Other Hedging Instruments (US Treasury Securities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Derivative [Line Items]
U.S. Treasury securities, net	$965	($2,936)
3 Year Maturity [Member] [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-900
5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-2,111
7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-339
10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	4,258
Fair Value Hedging [Member]
Derivative [Line Items]
U.S. Treasury securities, net	965	-2,936
Fair Value Hedging [Member] | 3 Year Maturity [Member] [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-902
Fair Value Hedging [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-2,116	-4,645
Fair Value Hedging [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-341	-718
Fair Value Hedging [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	4,324	2,427
At Par Value [Member]
Derivative [Line Items]
U.S. Treasury securities, net	908	-2,981
At Par Value [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net		-4,674
At Par Value [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net		-717
At Par Value [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net		2,410
At Cost Basis [Member]
Derivative [Line Items]
U.S. Treasury securities, net	974	-2,945
At Cost Basis [Member] | 3 Year Maturity [Member] [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-899
At Cost Basis [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-2,096	-4,650
At Cost Basis [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	-334	-717
At Cost Basis [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	$4,303	$2,422

Derivative_and_Other_Hedging_I7

Derivative and Other Hedging Instruments (TBA Securities by Coupon and Issuer) (Details) (TBA and Forward Settling Agency Securities [Member], USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Derivative [Line Items]
Derivative, Notional Amount	$4,873	$14,412
Cost Basis	4,815	14,576
Net long TBA position, at fair value	4,894	14,768
TBA, net carrying value	79	192
15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	-1,293	3,260
Cost Basis	-1,383	3,348
Net long TBA position, at fair value	-1,396	3,360
TBA, net carrying value	-13	12
30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	6,166	11,152
Cost Basis	6,198	11,228
Net long TBA position, at fair value	6,290	11,408
TBA, net carrying value	92	180
Fannie Mae [Member]
Derivative [Line Items]
Derivative, Notional Amount	2,230	15,127
Cost Basis	2,125	15,316
Net long TBA position, at fair value	2,178	15,509
TBA, net carrying value	53	193
Freddie Mac [Member]
Derivative [Line Items]
Derivative, Notional Amount	-957	-715
Cost Basis	-1,021	-740
Net long TBA position, at fair value	-1,025	-741
TBA, net carrying value	-4	-1
Ginnie Mae [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,600
Cost Basis	3,711
Net long TBA position, at fair value	3,741
TBA, net carrying value	30
2.5% Coupon [Member] | 15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	1,632	962
Cost Basis	1,670	968
Net long TBA position, at fair value	1,673	980
TBA, net carrying value	3	12
3.0% Coupon [Member] | 15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	-2,733	2,779
Cost Basis	-2,852	2,889
Net long TBA position, at fair value	-2,866	2,888
TBA, net carrying value	-14	-1
3.0% Coupon [Member] | 30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	5,432	5,254
Cost Basis	5,500	5,259
Net long TBA position, at fair value	5,566	5,313
TBA, net carrying value	66	54
3.5% Coupon [Member] | 15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	-192	-468
Cost Basis	-201	-495
Net long TBA position, at fair value	-203	-494
TBA, net carrying value	-2	1
3.5% Coupon [Member] | 30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	3,423	7,902
Cost Basis	3,560	8,151
Net long TBA position, at fair value	3,598	8,232
TBA, net carrying value	38	81
4.0% Coupon [Member] | 15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount		-13
Cost Basis		-14
Net long TBA position, at fair value		-14
TBA, net carrying value		0
4.0% Coupon [Member] | 30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	-2,689	-1,853
Cost Basis	-2,862	-2,019
Net long TBA position, at fair value	-2,874	-1,974
TBA, net carrying value	-12	45
4.5% Coupon [Member] | 30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount		-151
Cost Basis		-163
Net long TBA position, at fair value		-163
TBA, net carrying value		$0

Derivative_and_Other_Hedging_I8

Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Comprehensive Income Statement) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	($562)	($434)
Gain (loss) on REIT Equity Securities	2
Gain Loss on Other Debt	0	-3
Interest Only And Principal Only Strip [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Unrealized Gain (Loss) on Securities	11	12
Put Option [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Additions		-50
Settlement, Expirations or Exercise		50
Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	6,800
Additions	0	-1,000
Settlement, Expirations or Exercise	1,600	7,250
Notional Amount	5,200
Amount Gain/(Loss) Recognized in Income on Derivatives	-17	-105
TBA and Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	14,412	2,119
Additions	45,500	24,376
Settlement, Expirations or Exercise		-12,586
Notional Amount	4,873	13,909
Amount Gain/(Loss) Recognized in Income on Derivatives	234	60
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Settlement, Expirations or Exercise	-55,039
Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	43,700
Additions	-3,500	-5,900
Settlement, Expirations or Exercise	2,275	2,750
Notional Amount	44,925
Amount Gain/(Loss) Recognized in Income on Derivatives	-746	-380
Receiver Swaption [Member] | Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Additions	0	1,000
Settlement, Expirations or Exercise	-3,500
Amount Gain/(Loss) Recognized in Income on Derivatives	17
Future [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	-730	-1,730
Additions	-730	-730
Settlement, Expirations or Exercise	730	1,730
Notional Amount	-730	-730
Amount Gain/(Loss) Recognized in Income on Derivatives	-20	-36
Other derivative instruments [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives		2
Interest Only And Principal Only Strip [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives		49
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			-6,800	-14,250
Notional Amount	-5,200	-8,000	-6,800	-14,250
Not Designated as Hedging Instrument [Member] | Receiver Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			4,250
Notional Amount	750	1,000	4,250
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			-43,700	-43,250
Notional Amount	-44,925	-46,400	-43,700	-43,250
Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	-5,392	-2,007
Additions	-4,173	-7,241
Settlement, Expirations or Exercise	6,212	2,462
Notional Amount	-3,353	-6,786
Amount Gain/(Loss) Recognized in Income on Derivatives	-82	-45
Long [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Trading Securities	4,261
Long [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	52	72
Trading Securities		200	2,411	3,927
Trading Securities Added During the Period	15,562	1,900
Notional Amount Of Trading Securities Settlement Expiration During The Period	($13,712)	($5,627)

Pledged_Assets_Narrative_Detai

Pledged Assets (Narrative) (Details) (USD $)	Mar. 31, 2015
Pledged Assets [Abstract]
Risk of repurchase agreement to stockholders' equity	4.00%
Risk of interest swap and swaption agreements to stockholders' equity	$0.01

Pledged_Assets_Assets_Pledged_

Pledged Assets (Assets Pledged as Collateral) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	$56,836	$51,629
Accrued interest on pledged securities	182	153
Restricted cash	1,108	713
Total Fair Value Of Agency Securities Pledged And Accrued Interest	64,396	56,215
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	57,245	50,858
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	171	69
Accrued interest on pledged securities		2
Restricted cash	1,077	698
Total Fair Value Of Agency Securities Pledged And Accrued Interest	1,789	1,319
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Accrued interest on pledged securities	176	147
Total Fair Value Of Agency Securities Pledged And Accrued Interest	61,239	52,915
Variable Interest Entity, Primary Beneficiary [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	1,221	1,266
Accrued interest on pledged securities	4	4
Total Fair Value Of Agency Securities Pledged And Accrued Interest	1,225	1,270
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	141	702
Total Fair Value Of Agency Securities Pledged And Accrued Interest	143	711
Includes Sold But Not Yet Settled Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	58,778	52,895
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	4,328	2,454
US Treasury Securities [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	3,789	1,904
US Treasury Securities [Member] | Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	539	550
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash	29	6
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash	2	9
Excluding Cash Received [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash	$1,108	$713

Pledged_Assets_Securities_Pled

Pledged Assets (Securities Pledged as Collateral) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$62,255	$54,028
Agency Securities Pledged As Collateral Amortized Cost	61,301	53,477
Agency Securities Pledged As Collateral Accrued Interest	180	151
Maturity up to 30 days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	25,572	14,605
Agency Securities Pledged As Collateral Amortized Cost	25,188	14,453
Agency Securities Pledged As Collateral Accrued Interest	69	41
Maturity 31 To 59 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	11,932	10,912
Agency Securities Pledged As Collateral Amortized Cost	11,731	10,789
Agency Securities Pledged As Collateral Accrued Interest	32	30
Maturity 60 To 90 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	3,937	10,205
Agency Securities Pledged As Collateral Amortized Cost	3,880	10,109
Agency Securities Pledged As Collateral Accrued Interest	11	28
Maturity over 90 days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	17,025	16,402
Agency Securities Pledged As Collateral Amortized Cost	16,728	16,227
Agency Securities Pledged As Collateral Accrued Interest	47	47
Maturity Overnight [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	3,789	1,904
Agency Securities Pledged As Collateral Amortized Cost	3,774	1,899
Agency Securities Pledged As Collateral Accrued Interest	21	5
Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	58,466	52,124
Agency Securities Pledged As Collateral Amortized Cost	57,527	51,578
Agency Securities Pledged As Collateral Accrued Interest	$159	$146

Pledged_Assets_Assets_Pledged_1

Pledged Assets (Assets Pledged from Counterparties) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	$56,836	$51,629
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	3,363	5,363
Restricted Cash and Cash Equivalents	1,108	713
Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Securities Pledged	3,377	5,481
Restricted Cash and Cash Equivalents		28
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	14	43
Restricted Cash and Securities Pledged	14	118
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	4,328	2,454
US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	3,363	5,410
Reverse Repurchase Agreements [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	3,363	5,363
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	171	69
Restricted Cash and Cash Equivalents	1,077	698
Derivative [Member] | US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	539	550
Derivative [Member] | US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral		47
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents		$28

Pledged_Assets_Offsetting_Asse

Pledged Assets (Offsetting Assets and Liabilities) (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Millions, unless otherwise specified
Offsetting Assets and Liabilities [Line Items]
Collateral Received	($14)
Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	3,295	5,429
Net Amounts of Assets Presented in the Consolidated Balance Sheets	3,295	5,429
Financial Instruments	-3,272	-4,784
Collateral Received		-611
Net Amount	9	34
Assets [Member] | Interest Rate Swap [Member] | Swaption [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	120	211
Net Amounts of Assets Presented in the Consolidated Balance Sheets	120	211
Financial Instruments	-97	-94
Collateral Received	-14	-83
Net Amount	9	34
Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	59,420	51,176
Net Amounts of Assets Presented in the Consolidated Balance Sheets	59,420	51,176
Financial Instruments	-3,272	-4,784
Collateral Received	-56,145	-46,388
Liability [Member] | Interest Rate Swap [Member] | Swaption [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	1,308	880
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1,308	880
Financial Instruments	-97	-94
Collateral Received	-1,208	-782
Net Amount	3	4
Repurchase Agreements [Member] | Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	58,112	50,296
Net Amounts of Assets Presented in the Consolidated Balance Sheets	58,112	50,296
Financial Instruments	-3,175	-4,690
Collateral Received	-54,937	-45,606
Reverse Repurchase Agreements [Member] | Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	3,175	5,218
Net Amounts of Assets Presented in the Consolidated Balance Sheets	3,175	5,218
Financial Instruments	-3,175	-4,690
Collateral Received		($528)

Fair_Value_Measurements_Detail

Fair Value Measurements (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between hierarchy levels	0
Agency securities	$60,131	$55,482
Agency securities transferred to consolidated VIEs	1,221	1,266
U.S. Treasury securities	4,328	2,427
TBA securities	229	408
Debt of consolidated variable interest entities, at fair value	725	761
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	3,363	5,363
Interest rate swaps	229	408
REIT equity securities, at fair value	68	68
U.S. Treasury futures	1,352	890
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		5,363
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	4,396	2,495
Total liabilities	3,377	5,368
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	61,581	57,156
Total liabilities	2,063	1,646
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]
TBA securities	30	5
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	50	75
Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
U.S. Treasury futures	1,308	880
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps	70	136
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]
Interest rate swaps	1,308	880
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps		197
U.S. Treasury futures	30	5
Purchases Of TBAs And Forward Settling Agency Securities [Member] | 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]
TBA securities	109	197
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]
U.S. Treasury futures	$14	$5

Stockholders_Equity_Preferred_

Stockholders' Equity (Preferred Stock) (Details) (USD $)	3 Months Ended	12 Months Ended	3 Months Ended	1 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2014	Mar. 31, 2015	31-May-14	Apr. 30, 2012	5-May-14
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Authorized		10,000,000	10,000,000
Preferred Stock Authorized, but not Issued			3,100,000
Preferred Stock, Shares Issued		6,900,000	6,900,000
Preferred Stock, Value, Issued		336	336
Preferred Class A [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Capital Shares Reserved for Future Issuance			6,900,000
Sale of Stock, Price Per Share					$24.21
Series A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Dividend Rate, Percentage		8.00%
Issuance of preferred stock	167
Preferred Stock, Liquidation Preference Per Share			25
Preferred Class B [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Capital Shares Reserved for Future Issuance			8,050
Preferred Stock, Dividend Rate, Percentage			7.75%
Preferred Stock, Shares Issued						7,000,000
Share Price						$24.21
Preferred Stock, Value, Issued						$169
Series B Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Liquidation Preference Per Share						$25
Preferred stock, percent interest per share				0.10%

Stockholders_Equity_Common_Sto

Stockholders' Equity (Common Stock Repurchase Program) (Details) (USD $)	3 Months Ended		12 Months Ended
In Millions, except Per Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Average repurchase price (in dollars per share)	$22.10
Repurchase of common stock, value		$74	$74
Remaining amount authorized for repurchase	$992
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock shares	3.4	3.4

Stockholders_Equity_Accumulate

Stockholders' Equity (Accumulated Other Comprehensive Income (Loss)) (Details) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Accumulated OCI Balance	$850	($819)	$430	($1,383)
OCI before reclassifications	391	521
Amounts reclassified from accumulated OCI	29	43
Total Accumulated OCI Balance	-7	62
Agency Securities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning OCI Balance	570	-1,087
OCI before reclassifications	427	502
Amounts reclassified from accumulated OCI	-36	19
Ending OCI Balance	961	-566
Discontinuation of Election to Account for Interest Rate Swaps as Designated Cash Flow Hedges [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Net Unrealized Gain (Loss) on Swaps	-111	253	-140	-296
Interest Rate Swap [Member] | Agency Securities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
OCI before reclassifications	$427	$502

Subsequent_Event_Details

Subsequent Event (Details) (USD $)	3 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Apr. 27, 2015	Apr. 13, 2015
Subsequent Event [Line Items]
Dividends declared per common share	$0.66	$0.65
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends declared per common share			$0.20	$0.22