AGNC Investment (AGNC) 10-Q 7 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1
Entity Registrant Name	AGNC Investment Corp.
Entity Central Index Key	1,423,689
Entity Filer Category	Large Accelerated Filer
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		391,327,480
Trading Symbol	AGNC

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Assets:
Agency securities, at fair value (including pledged securities of $51,434 and $53,055, respectively)	$ 54,141	$ 55,506
Agency securities transferred to consolidated variable interest entities, at fair value (pledged securities)	621	662
Credit risk transfer securities, at fair value	884	876
Non-Agency securities, at fair value	36	36
U.S. Treasury securities, at fair value	224	0
REIT equity securities, at fair value	42	29
Cash and cash equivalents	972	1,046
Restricted cash and cash equivalents	386	317
Derivative assets, at fair value	410	205
Receivable under reverse repurchase agreements	10,770	10,961
Goodwill and other intangible assets, net	550	551
Other assets	185	187
Total assets	69,221	70,376
Liabilities:
Repurchase Agreements	48,956	50,296
Debt of consolidated variable interest entities, at fair value	336	357
Payable for investment securities purchased	457	95
Derivative liabilities, at fair value	32	28
Dividends payable	80	80
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	10,352	10,467
Accounts payable and other liabilities	670	299
Total liabilities	60,883	61,622
Stockholders' equity:
7.750% Series B Cumulative Redeemable Preferred Stock (aggregate liquidation preference of $175)	169	169
7.000% Series C Fixed-to-Floating Rate Cumulative Redeemable Preferred Stock (aggregate liquidation preference of $325)	315	315
Common stock - $0.01 par value; 600.0 shares authorized; 391.3 shares issued and outstanding	4	4
Additional paid-in capital	11,174	11,173
Retained deficit	(2,358)	(2,562)
Accumulated other comprehensive loss	(966)	(345)
Total stockholders' equity	8,338	8,754
Total liabilities and stockholders' equity	$ 69,221	$ 70,376

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Millions, $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred Stock A, Liquidation Preference, Value	$ 0	$ 0
Available-for-sale Securities Pledged as Collateral	$ 51,434	53,055
Preferred Stock, Shares Authorized	10
Preferred Stock B, Liquidation Preference, Value	$ 175	175
Preferred Stock C, Liquidation Preference, Value	$ 325	$ 325
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	391.3	391.3
Common Stock, Shares, Outstanding	391.3	391.3
Non-Agency Securities Pledged as Collateral	$ 0	$ 0
Trading Securities Pledged as Collateral	0	0
Assets Pledged included in Receivable for Securities Sold	$ 0	$ 0

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Dividends declared per common share	$ 0.54	$ 0.54
Interest income:
Interest income	$ 431	$ 296
Interest expense	206	98
Net interest income	225	198
Other gain (loss), net:
Loss on sale of investment securities, net	(2)	(84)
Unrealized gain (loss) on investment securities measured at fair value through net income, net	(523)	16
Gain (loss) on derivative instruments and other securities, net	738	(40)
Management fee income	4	4
Total other gain (loss), net:	217	(104)
Expenses:
Compensation and benefits	10	10
Other operating expenses	8	8
Total operating expenses	18	18
Net income	424	76
Dividend on preferred stock	9	7
Net income available to common stockholders	415	69
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	621	(46)
Comprehensive income (loss)	(197)	122
Comprehensive income (loss) available (attributable) to common stockholders	$ (206)	$ 115
Weighted average number of common shares outstanding - basic	391.3	331
Weighted average number of common shares outstanding - diluted	391.5	331.1
Net income per common share - basic and diluted	$ 1.06	$ 0.21

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Series A Preferred Stock [Member]Preferred Stock [Member]	Series B Preferred Stock [Member]Preferred Stock [Member]	Series C Preferred Stock [Member]Preferred Stock [Member]
Balance, value at Dec. 31, 2016	$ 7,356	$ 3	$ 9,932	$ (2,518)	$ (397)	$ 167	$ 169	$ 0
Balance, Common Stock, shares at Dec. 31, 2016		331
Net income (loss)	76			76
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	46				46
Preferred dividends declared	(7)			7
Common dividends declared	(179)			(179)
Balance, value at Mar. 31, 2017	7,292	$ 3	9,932	(2,628)	(351)	167	169	0
Balance, Common Stock, shares at Mar. 31, 2017		331
Balance, value at Dec. 31, 2016	$ 7,356	$ 3	9,932	(2,518)	(397)	167	169	0
Balance, Common Stock, shares at Dec. 31, 2016		331
Other comprehensive income (loss):
Stock Issued During Period, Shares, New Issues	7.6
Stock Issued During Period, Value, New Issues	$ 0
Balance, value at Dec. 31, 2017	$ 8,754	$ 4	11,173	(2,562)	(345)	0	169	315
Balance, Common Stock, shares at Dec. 31, 2017	391.3	391.3
Net income (loss)	$ 424			424
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	(621)				(621)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	1		1
Preferred dividends declared	(9)			(9)
Common dividends declared	(211)			(211)
Balance, value at Mar. 31, 2018	$ 8,338	$ 4	$ 11,174	$ (2,358)	$ (966)	$ 0	$ 169	$ 315
Balance, Common Stock, shares at Mar. 31, 2018	391.3	391.3

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Cash Flows [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 1,358	$ 1,292
Operating activities:
Net income (loss)	424	76
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of premiums and discounts on mortgage-backed securities, net	69	89
Amortization of intangible assets	1	1
Stock based compensation	1	0
Loss on sale of investment securities, net	2	84
Unrealized (gain) loss on investment securities measured at fair value through net income, net	523	(16)
(Gain) loss on derivative instruments and other securities, net	(738)	40
Decrease in other assets	3	125
Increase (decrease) in accounts payable and other accrued liabilities	3	(9)
Net cash provided by operating activities	288	390
Investing activities:
Purchases of Agency mortgage-backed securities	(2,287)	(4,573)
Purchases of credit risk transfer and non-Agency securities	(215)	(317)
Proceeds from sale of Agency mortgage-backed securities	1,181	4,424
Proceeds from sale of credit risk transfer and non-Agency securities	208	193
Principal collections on Agency mortgage-backed securities	1,661	1,636
Principal collections on credit risk transfer and non-Agency securities	0	4
Payments on U.S. Treasury securities	(1,345)	(1,748)
Proceeds from U.S. Treasury securities	1,403	2,999
Net proceeds from (payments on) reverse repurchase agreements	231	(1,192)
Net proceeds from (payments on) derivative instruments	466	(72)
Purchases of REIT equity securities	(16)	0
Net cash provided by (used in) investing activities	1,287	1,354
Financing activities:
Proceeds from repurchase arrangements	243,168	77,864
Payments on repurchase agreements	(244,507)	(76,347)
Payments on Federal Home Loan Bank advances	0	(3,037)
Payments on debt of consolidated variable interest entities	(21)	(28)
Cash dividends paid	(220)	(186)
Net cash provided by (used in) financing activities	(1,580)	(1,734)
Net change in cash and cash equivalents	(5)	$ 10
Cash and cash equivalents at end of period	$ 972

Unaudited Interim Consolidated

Unaudited Interim Consolidated Financial Statements	3 Months Ended
	Mar. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information [Text Block]	Basis of Presentation The unaudited interim consolidated financial statements of AGNC Investment 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. 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. Our unaudited interim consolidated financial statements include the accounts of all of our wholly-owned subsidiaries and variable interest entities for which we are the primary beneficiary. Significant intercompany accounts and transactions have been eliminated. Adoption of Accounting Standard Updates As of January 1, 2018, we adopted Accounting Standards Update ("ASU") 2014-09, Revenue from Contracts with Customers (Topic 606), and ASU 2016-18 , Statement of Cash Flows (Topic 230) - Restricted Cash. The adoption of ASU 2014-09 resulted in reclassification of expense reimbursements from MTGE Investment Corp. ("MTGE") from an other operating expense offset to management fee income on the consolidated statements of comprehensive income. Net income was not impacted. The adoption of ASU 2016-18 resulted in the presentation of restricted cash with cash and cash equivalents on the consolidated statements of cash flows when reconciling the total beginning and ending amounts. Our prior period results have been revised to conform to the current presentation.

Organization

Organization	3 Months Ended
	Mar. 31, 2018
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. Our common stock is traded on The Nasdaq Global Select Market under the symbol "AGNC." We operate 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 income. So 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 income to the extent that we distribute our annual taxable income to our stockholders on a timely basis. It is our intention to distribute 100% of our taxable income, after application of available tax attributes, within the limits prescribed by the Internal Revenue Code, which may extend into the subsequent tax year. We earn income primarily from investing in Agency residential mortgage-backed securities ("Agency RMBS") for which the principal and interest payments are guaranteed by a U.S. Government-sponsored enterprise or a U.S. Government agency. We may also invest in other types of mortgage and mortgage-related securities, such as credit risk transfer ("CRT") securities and non-Agency residential and commercial mortgage-backed securities ("non-Agency RMBS" and "CMBS," respectively), where repayment of principal and interest is not guaranteed by a U.S. Government-sponsored enterprise or U.S. Government agency. We fund our investments primarily through borrowings structured as repurchase agreements. Our principal objective is to provide our stockholders with attractive risk-adjusted returns through a combination of monthly dividends and tangible net book value accretion. We generate income from the interest earned on our investments, net of associated borrowing and hedging costs, and net realized gains and losses on our investment and hedging activities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Investment Securities Agency RMBS consist of residential mortgage pass-through securities and collateralized mortgage obligations ("CMOs") guaranteed by the Federal National Mortgage Association ("Fannie Mae"), Federal Home Loan Mortgage Corporation ("Freddie Mac," and together with Fannie Mae, the "GSEs") or the Government National Mortgage Association ("Ginnie Mae"). CRT securities are risk sharing instruments issued by the GSEs, and similarly structured transactions issued by third-party market participants, that transfer a portion of the risk associated with credit losses within pools of conventional residential mortgage loans from the GSEs and/or third parties to private investors. Unlike Agency RMBS, full repayment of the original principal balance of CRT securities is not guaranteed by a GSE or U.S. Government agency; rather, "credit risk transfer" is achieved by writing down the outstanding principal balance of the CRT securities if credit losses on a related pool of loans exceed certain thresholds. By reducing the amount that they are obligated to repay to holders of CRT securities, the GSEs and/or other third parties offset credit losses on the related loans. Non-Agency RMBS and CMBS (together, "Non-Agency MBS") are backed by residential and commercial mortgage loans, respectively, packaged and securitized by a private institution, such as a commercial bank. Non-Agency MBS typically benefit from credit enhancements derived from structural elements, such as subordination, overcollateralization or insurance, but nonetheless carry a higher level of credit exposure than Agency RMBS. Mortgage-related securities may also include investments in the common stock of other publicly traded mortgage REITs, including MTGE, that primarily invest in Agency securities, non-Agency securities, other mortgage related instruments and/or real estate on a leveraged basis. As of March 31, 2018 , our investments in REIT equity securities consisted solely of MTGE common stock. Accounting Standards Codification ("ASC") Topic 320, Investments—Debt and Equity Securities , 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. Alternatively, we may elect the fair value option of accounting for such securities pursuant to ASC Topic 825, Financial Instruments . All of our securities are reported at fair value as they have either been designated as available-for-sale or trading or we have elected the fair value option of accounting. Unrealized gains and losses on securities classified as available-for-sale are reported in accumulated other comprehensive income ("OCI"). Unrealized gains and losses on securities classified as trading or for which we elected the fair value option are reported in net income through other gain (loss) during the period in which they occur. Upon the sale of a security designated as available-for-sale, 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. Prior to fiscal year 2017, we primarily designated our investment securities as available-for-sale. On January 1, 2017, we began electing the fair value option of accounting for all investment securities acquired after fiscal year 2016. In our view, this election simplifies the accounting for investment securities and more appropriately reflects the results of our operations for a particular reporting period, as the fair value changes for these assets are presented in a manner consistent with the presentation and timing of the fair value changes of our hedging instruments. We are not permitted to change the designation of securities acquired prior to January 1, 2017; accordingly, such securities will continue to be classified as available-for-sale securities until we receive full repayment of principal or we dispose of the security. We estimate the fair value of our investment securities based on prices provided by multiple third-party pricing services and non-binding dealer quotes (collectively "pricing sources"). These pricing sources use various valuation approaches, including market and income approaches, using "Level 2" inputs. The pricing sources primarily utilize a matrix pricing technique that interpolates the estimated fair value of our Agency RMBS based on observed quoted prices for forward contracts in the Agency RMBS "to-be-announced" market ("TBA securities") of the same coupon, maturity and issuer, adjusted to reflect the specific characteristics of the pool of mortgages underlying the Agency security, which may include maximum loan balance, loan vintage, loan-to-value ratio, geography and other characteristics as may be appropriate. The pricing sources may also utilize discounted cash flow model-derived pricing techniques to estimate the fair value of investment securities. Such models incorporate market-based discount rate assumptions based on observable inputs such as recent trading activity, credit data, volatility statistics, benchmark interest rate curves and other market data that are current as of the measurement date and may include certain unobservable inputs, such as assumptions of future levels of prepayment, defaults and loss severities. We review the pricing estimates obtained from the pricing sources and perform procedures to validate their reasonableness. Refer to Note 8 for further discussion of fair value measurements. We evaluate our investments designated as available-for-sale 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 Agency RMBS and non-Agency MBS of high credit quality 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 . We estimate long-term prepayment speeds of our mortgage securities using a third-party service and market data. The third-party service provider estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates, mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, interest rate 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 third-party estimates and, based on our judgment, we may adjust the estimates. We review our actual and anticipated prepayment experience on at least a quarterly basis and effective yields are recalculated when differences arise between (i) our previously estimated future prepayments and (ii) actual prepayments to date and our current estimated future prepayments. If the actual and estimated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. At the time we purchase CRT securities and non-Agency MBS that are not of high credit quality, we determine an effective yield based on our estimate of the timing and amount of future cash flows and our cost basis. Our initial cash flow estimates for these investments are based on our observations of current information and events and include assumptions related to interest rates, prepayment rates and the impact of default and severity rates on the timing and amount of credit losses. On at least a quarterly basis, we review the estimated cash flows and make appropriate adjustments, based on inputs and analysis received from external sources, internal models, and our judgment regarding such inputs and other factors. Any resulting changes in effective yield are recognized prospectively based on the current amortized cost of the investment as adjusted for credit impairment, if any. Repurchase Agreements We finance the acquisition of securities for our investment portfolio primarily through repurchase transactions under master repurchase agreements. Pursuant to ASC Topic 860, Transfers and Servicing , we account for repurchase transactions as collateralized financing transactions, which are carried at their contractual amounts (cost), plus accrued interest. Our repurchase agreements typically have maturities of less than one year, but may extend up to five years or more. Interest rates on our repurchase agreements generally correspond to one or three-month LIBOR plus or minus a fixed spread. The fair value of our repurchase agreements is assumed to equal cost as the interest rates are considered to be at market. Reverse Repurchase Agreements and Obligation to Return Securities Borrowed under Reverse Repurchase Agreements We borrow securities to cover short sales of U.S. Treasury securities through reverse repurchase transactions under our master repurchase agreements (see Derivative Instruments below). 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. Our reverse repurchase agreements typically have maturities of 30 days or less. The fair value of our reverse repurchase agreements is assumed to equal cost as the interest rates generally reset daily. Derivative Instruments We use a variety of derivative instruments to hedge a portion of our exposure to market risks, including interest rate, prepayment, extension and liquidity risks. 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 primary instruments that we use are interest rate swaps, options to enter into interest rate swaps ("swaptions"), U.S. Treasury securities and U.S. Treasury futures contracts. We also use forward contracts in the Agency RMBS "to-be-announced" market, or TBA securities, to invest in and finance Agency securities as well as to periodically reduce our exposure to Agency RMBS. 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 our accompanying consolidated balance sheets 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 if the counterparties to these instruments fail to perform their obligations under the contracts. Our derivative agreements require that we post or receive collateral to mitigate such risk. We also attempt to minimize our risk of loss by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to hedge the variable cash flows associated with our borrowings made under repurchase agreements. Under our interest rate swap agreements, we typically pay a fixed rate and receive a floating rate based on one or three-month LIBOR ("payer swaps") with terms up to 20 years. Our swap agreements are privately negotiated in the over-the-counter ("OTC") market. The majority of our interest rate swaps are centrally cleared through a registered commodities exchange. We value centrally cleared interest rate swaps using the daily settlement price, or fair value, determined by the clearing exchange based on a pricing model that references observable market inputs, including LIBOR, swap rates and the forward yield curve. Our centrally cleared swaps require that we post an "initial margin" amount determined by the clearing exchange, which is generally intended to be set at a level sufficient to protect the exchange from the interest rate swap's maximum estimated single-day price movement. We also exchange daily settlements of "variation margin" based upon changes in fair value, as measured by the exchange. Pursuant to rules governing central clearing activities, we recognize variation margin settlements as a direct reduction of the carrying value of the interest rate swap asset or liability. We value non-centrally cleared swaps using a combination of third-party valuations obtained from pricing services and the swap counterparty. The third-party valuations are model-driven using observable inputs, including LIBOR, swap rates and the forward yield curve. We also consider both our own and our counterparties' nonperformance risk in estimating the fair value of our interest rate swaps. In considering the effect of nonperformance risk, we assess the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We purchase interest rate swaptions to help mitigate the potential impact of larger, 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 ("payer swaptions"). We may also enter into swaption agreements that provide us the option to enter into a receive-fixed interest rate swap ("receiver swaptions"). Our interest rate swaption agreements are privately negotiated in the OTC market and are not subject to central clearing. The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. We estimate the fair value of interest rate swaptions using a combination of inputs from counterparty and third-party pricing models based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option, adjusted for non-performance risk, if any. The difference between the premium paid 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. TBA securities A TBA security is a forward contract for the purchase or sale of Agency RMBS at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific Agency RMBS to be delivered into the contract are not known until shortly before the settlement date. We may choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting TBA position, net settling the offsetting positions for cash, and simultaneously purchasing or selling a similar TBA contract for a later settlement date (together referred to as a "dollar roll transaction"). The Agency securities purchased or sold for a forward settlement date are typically priced at a discount to equivalent securities settling in the current month. This difference, or "price drop," is the economic equivalent to interest income on the underlying Agency securities, less an implied funding cost, over the forward settlement period (referred to as "dollar roll income"). Consequently, forward purchases of Agency securities and dollar roll transactions represent a form of off-balance sheet financing. We account for 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 physically settle the TBA contract on the settlement date. We account for TBA dollar roll transactions as a series of derivative transactions. Gains, losses and dollar roll income associated with our TBA contracts are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. We estimate the fair value of TBA securities based on similar methods used to value our Agency RMBS securities. U.S. Treasury securities We purchase and 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 our accompanying consolidated balance sheets 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. Loss Contingencies We evaluate the existence of any pending or threatened litigation or other potential claims against the Company in accordance with ASC Topic 450, Contingencies, which requires that we assess the likelihood and range of potential outcomes of any such matters. We are the defendant in three stockholder derivative lawsuits alleging that certain of our current and former directors and officers breached fiduciary duties and wasted corporate assets relating to past renewals of the management agreement with our former external manager and the internalization of our management, which occurred on July 1, 2016. Although the outcomes of these cases cannot be predicted with certainty, we do not believe that these cases have merit or will result in a material liability, and, as of March 31, 2018 , we did not accrue a loss contingency related to these matters. Recent Accounting Pronouncements We consider the applicability and impact of all Accounting Standards Updates ("ASUs") issued by the Financial Accounting Standards Board. ASUs not listed below were determined to be either not applicable, are not expected to have a significant impact on our consolidated financial statements when adopted, or did not have a significant impact on our consolidated financial statements upon adoption. ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): ASU 2016-13 changes the impairment model for most financial assets and certain other instruments. Allowances for credit losses on available-for-sale debt securities will be recognized, rather than direct reductions in the amortized cost of the investments. The new model also requires the estimation of lifetime expected credit losses and corresponding recognition of allowance for losses on trade and other receivables, held-to-maturity debt securities, loans, and other instruments held at amortized cost. The ASU requires certain recurring disclosures and is effective for annual periods, and interim periods within those annual periods, beginning on or after December 15, 2019, with early adoption permitted for annual periods, and interim periods within those annual periods, beginning on or after December 15, 2018. ASU 2016-13 is not expected to have a significant impact on our consolidated financial statements.

Investment Securities

Investment Securities	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	3 years and ≤ 5 years 6,283 6,395 3.23% 2.36% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 42,171 43,513 3.75% 2.98% 45,977 46,398 3.75% 2.95% > 10 years 4,557 4,620 3.79% 3.52% 892 857 4.87% 4.74% Total $ 55,682 $ 57,211 3.70% 2.93% $ 57,080 $ 57,466 3.71% 2.89% The following table presents the gross unrealized loss and fair values of securities classified as available-for-sale by length of time that such securities have been in a continuous unrealized loss position as of March 31, 2018 and December 31, 2017 (in millions): Unrealized Loss Position For Less than 12 Months 12 Months or More Total Securities Classified as Available-for-Sale Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 $ 9,782 $ (133 ) $ 18,946 $ (853 ) $ 28,728 $ (986 ) December 31, 2017 $ 3,582 $ (15 ) $ 20,577 $ (451 ) $ 24,159 $ (466 ) We did not recognize OTTI charges on our investment securities for the three months ended March 31, 2018 and 2017 . As of the end of each respective reporting period, a decision had not been made to sell any of our securities in an unrealized loss position and we did not believe it was more likely than not that we would be required to sell such securities before recovery of their amortized cost basis. The unrealized losses on our securities were not due to credit losses given the GSE or U.S. Government agency guarantees, but rather were due to changes in interest rates and prepayment expectations. However, as we continue to actively manage our portfolio, we may recognize additional realized losses on our investment securities upon selecting specific securities to sell. Gains and Losses on Sale of Investment Securities The following table is a summary of our net gain (loss) from the sale of investment securities for the three months ended March 31, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended March 31, 2018 2017 Investment Securities Available-for-Sale Securities 2 Fair Value Option Securities Total Available-for-Sale Securities 2 Fair Value Option Securities Total Investment securities sold, at cost $ (387 ) $ (1,003 ) $ (1,390 ) $ (5,149 ) $ (219 ) $ (5,368 ) Proceeds from investment securities sold 1 388 1,000 1,388 5,065 219 5,284 Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) Gross gain on sale of investment securities $ 3 $ 7 $ 10 $ 4 $ — $ 4 Gross loss on sale of investment securities (2 ) (10 ) (12 ) (88 ) — (88 ) Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) ________________________________ 1. Proceeds include cash received during the period, plus receivable for investment securities sold during the period as of period end. 2. See Note 10 for a summary of changes in accumulated OCI. Securitizations and Variable Interest Entities As of March 31, 2018 and December 31, 2017 , 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 RMBS. 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 and approximate unpaid principal balance of $0.6 billion and $0.7 billion as of March 31, 2018 and December 31, 2017 , respectively, and debt with a total fair value and approximate unpaid principal balance of $0.3 billion and $0.4 billion , respectively, in our accompanying consolidated balance sheets. 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. Our involvement with the consolidated trusts is limited to the Agency securities transferred by us upon the formation of the trusts and the CMO securities subsequently held by us. There are no arrangements that could require us to provide financial support to the trusts. As of March 31, 2018 and December 31, 2017 , the fair value of our CMO securities and interest and principal-only securities was $0.8 billion and $0.9 billion , respectively, excluding the consolidated CMO trusts discussed above, or $1.1 billion and $1.2 billion , respectively, 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 $91 million and $124 million as of March 31, 2018 and December 31, 2017 , respectively." id="sjs-B4">Investment Securities As of March 31, 2018 and December 31, 2017 , our investment portfolio consisted of $55.7 billion and $57.1 billion of investment securities, at fair value, respectively, and $13.6 billion and $15.7 billion of TBA securities, at fair value, respectively. Our TBA position is reported at its net carrying value of $82 million and $3 million as of March 31, 2018 and December 31, 2017 , 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. As of March 31, 2018 and December 31, 2017 , our investment securities had a net unamortized premium balance of $2.6 billion and $2.7 billion , respectively, including interest and principal-only securities. The following tables summarize our investment securities as of March 31, 2018 and December 31, 2017 , excluding TBA securities, (dollars in millions). Details of our TBA securities as of each of the respective dates are included in Note 6 . March 31, 2018 December 31, 2017 Investment Securities Amortized Cost Fair Value Amortized Fair Value Agency RMBS: Fixed rate $ 55,266 $ 53,696 $ 55,477 $ 55,026 Adjustable rate 265 268 278 283 CMO 595 590 629 631 Interest-only and principal-only strips 202 208 213 228 Total Agency RMBS 56,328 54,762 56,597 56,168 Non-Agency RMBS 7 7 7 7 CMBS 28 29 28 29 CRT securities 848 884 834 876 Total investment securities $ 57,211 $ 55,682 $ 57,466 $ 57,080 March 31, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 22,893 $ 7,430 $ 32 $ 7 $ — $ — $ 30,362 Unamortized discount (24 ) (3 ) — — — — (27 ) Unamortized premium 1,083 414 — — — — 1,497 Amortized cost 23,952 7,841 32 7 — — 31,832 Gross unrealized gains 13 6 1 — — — 20 Gross unrealized losses (713 ) (273 ) — — — — (986 ) Total available-for-sale securities, at fair value 23,252 7,574 33 7 — — 30,866 Securities remeasured at fair value through earnings: Par value 13,472 9,948 — — 29 814 24,263 Unamortized discount (33 ) (2 ) — — (1 ) (1 ) (37 ) Unamortized premium 672 446 — — — 35 1,153 Amortized cost 14,111 10,392 — — 28 848 25,379 Gross unrealized gains 11 5 — — 1 37 54 Gross unrealized losses (360 ) (256 ) — — — (1 ) (617 ) Total securities remeasured at fair value through earnings 13,762 10,141 — — 29 884 24,816 Total securities, at fair value $ 37,014 $ 17,715 $ 33 $ 7 $ 29 $ 884 $ 55,682 Weighted average coupon as of March 31, 2018 3.66 % 3.69 % 2.87 % 2.50 % 6.55 % 5.50 % 3.70 % Weighted average yield as of March 31, 2018 1 2.88 % 2.93 % 2.02 % 3.03 % 7.36 % 5.51 % 2.93 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 7.6% based on forward rates as of March 31, 2018 . December 31, 2017 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 24,200 $ 8,219 $ 34 $ 7 $ — $ — $ 32,460 Unamortized discount (25 ) (3 ) — — — — (28 ) Unamortized premium 1,119 447 — — — — 1,566 Amortized cost 25,294 8,663 34 7 — — 33,998 Gross unrealized gains 98 22 1 — — — 121 Gross unrealized losses (325 ) (141 ) — — — — (466 ) Total available-for-sale securities, at fair value 25,067 8,544 35 7 — — 33,653 Securities remeasured at fair value through earnings: Par value 13,558 7,956 — — 29 801 22,344 Unamortized discount (34 ) — — — (1 ) — (35 ) Unamortized premium 711 415 — — — 33 1,159 Amortized cost 14,235 8,371 — — 28 834 23,468 Gross unrealized gains 26 2 — — 1 42 71 Gross unrealized losses (70 ) (42 ) — — — — (112 ) Total securities remeasured at fair value through earnings 14,191 8,331 — — 29 876 23,427 Total securities, at fair value $ 39,258 $ 16,875 $ 35 $ 7 $ 29 $ 876 $ 57,080 Weighted average coupon as of December 31, 2017 3.67 % 3.73 % 2.84 % 2.50 % 6.55 % 5.26 % 3.71 % Weighted average yield as of December 31, 2017 1 2.84 % 2.87 % 2.02 % 3.08 % 7.30 % 5.19 % 2.89 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 8.4% based on forward rates as of December 31, 2017 . As of March 31, 2018 and December 31, 2017 , our investments in CRT and non-Agency securities had the following credit ratings: March 31, 2018 December 31, 2017 CRT and Non-Agency Security Credit Ratings 1 CRT RMBS CMBS CRT RMBS CMBS AAA $ — $ 7 $ — $ — $ 7 $ — BBB 26 — 29 20 — 29 BB 139 — — 136 — — B 698 — — 691 — — Not Rated 21 — — 29 — — Total $ 884 $ 7 $ 29 $ 876 $ 7 $ 29 ________________________________ 1. Represents the lowest of Standard and Poor's ("S&P"), Moody's and Fitch credit ratings, stated in terms of the S&P equivalent rating as of each date. Our CRT securities reference the performance of loans underlying Agency RMBS issued by Fannie Mae or Freddie Mac, which were subject to their underwriting standards. As of March 31, 2018 , our CRT securities had floating and fixed rate coupons ranging from 3.7% to 8.8% , referenced to loans originated between 2012 and 2018 with weighted average coupons ranging from 3.6% to 4.4% . As of December 31, 2017 , our CRT securities had floating rate coupons ranging from 3.9% to 8.5% , referenced to loans originated between 2012 and 2017 with weighted average coupons ranging from 3.6% to 4.4% . The actual maturities of our investment securities are generally shorter than their 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, 2018 and December 31, 2017 , the weighted average expected constant prepayment rate ("CPR") over the remaining life of our aggregate investment portfolio was 7.6% and 8.4% , respectively. Our estimates can differ materially for different securities and thus our individual holdings have a wide range of projected CPRs. The following table summarizes our investments as of March 31, 2018 and December 31, 2017 according to their estimated weighted average life classification (dollars in millions): March 31, 2018 December 31, 2017 Estimated Weighted Average Life of Investment Securities Fair Value Amortized Cost Weighted Average Coupon Weighted Average Yield Fair Value Amortized Cost Weighted Average Coupon Weighted Average Yield ≥ 1 year and ≤ 3 years $ 2,671 $ 2,683 3.91% 2.61% $ 2,712 $ 2,693 3.90% 2.67% > 3 years and ≤ 5 years 6,283 6,395 3.23% 2.36% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 42,171 43,513 3.75% 2.98% 45,977 46,398 3.75% 2.95% > 10 years 4,557 4,620 3.79% 3.52% 892 857 4.87% 4.74% Total $ 55,682 $ 57,211 3.70% 2.93% $ 57,080 $ 57,466 3.71% 2.89% The following table presents the gross unrealized loss and fair values of securities classified as available-for-sale by length of time that such securities have been in a continuous unrealized loss position as of March 31, 2018 and December 31, 2017 (in millions): Unrealized Loss Position For Less than 12 Months 12 Months or More Total Securities Classified as Available-for-Sale Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 $ 9,782 $ (133 ) $ 18,946 $ (853 ) $ 28,728 $ (986 ) December 31, 2017 $ 3,582 $ (15 ) $ 20,577 $ (451 ) $ 24,159 $ (466 ) We did not recognize OTTI charges on our investment securities for the three months ended March 31, 2018 and 2017 . As of the end of each respective reporting period, a decision had not been made to sell any of our securities in an unrealized loss position and we did not believe it was more likely than not that we would be required to sell such securities before recovery of their amortized cost basis. The unrealized losses on our securities were not due to credit losses given the GSE or U.S. Government agency guarantees, but rather were due to changes in interest rates and prepayment expectations. However, as we continue to actively manage our portfolio, we may recognize additional realized losses on our investment securities upon selecting specific securities to sell. Gains and Losses on Sale of Investment Securities The following table is a summary of our net gain (loss) from the sale of investment securities for the three months ended March 31, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended March 31, 2018 2017 Investment Securities Available-for-Sale Securities 2 Fair Value Option Securities Total Available-for-Sale Securities 2 Fair Value Option Securities Total Investment securities sold, at cost $ (387 ) $ (1,003 ) $ (1,390 ) $ (5,149 ) $ (219 ) $ (5,368 ) Proceeds from investment securities sold 1 388 1,000 1,388 5,065 219 5,284 Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) Gross gain on sale of investment securities $ 3 $ 7 $ 10 $ 4 $ — $ 4 Gross loss on sale of investment securities (2 ) (10 ) (12 ) (88 ) — (88 ) Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) ________________________________ 1. Proceeds include cash received during the period, plus receivable for investment securities sold during the period as of period end. 2. See Note 10 for a summary of changes in accumulated OCI. Securitizations and Variable Interest Entities As of March 31, 2018 and December 31, 2017 , 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 RMBS. 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 and approximate unpaid principal balance of $0.6 billion and $0.7 billion as of March 31, 2018 and December 31, 2017 , respectively, and debt with a total fair value and approximate unpaid principal balance of $0.3 billion and $0.4 billion , respectively, in our accompanying consolidated balance sheets. 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. Our involvement with the consolidated trusts is limited to the Agency securities transferred by us upon the formation of the trusts and the CMO securities subsequently held by us. There are no arrangements that could require us to provide financial support to the trusts. As of March 31, 2018 and December 31, 2017 , the fair value of our CMO securities and interest and principal-only securities was $0.8 billion and $0.9 billion , respectively, excluding the consolidated CMO trusts discussed above, or $1.1 billion and $1.2 billion , respectively, 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 $91 million and $124 million as of March 31, 2018 and December 31, 2017 , respectively.

Repurchase Agreements And Other

Repurchase Agreements And Other Debt	3 Months Ended
	Mar. 31, 2018
Disclosure of Repurchase Agreements [Abstract]
Repurchase Agreements And Other Debt	1 to ≤ 3 months 12,881 1.70 % 57 16,150 1.50 % 50 > 3 to ≤ 6 months 3,381 1.76 % 134 7,287 1.50 % 130 > 6 to ≤ 9 months 485 2.07 % 214 2,361 1.66 % 225 > 9 to ≤ 12 months 3,678 1.96 % 297 202 1.64 % 297 > 12 to ≤ 24 months 2,267 2.29 % 596 1,700 1.84 % 468 > 24 to ≤ 36 months 1,325 2.26 % 937 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 48,956 1.82 % 109 $ 50,296 1.57 % 116 As of March 31, 2018 and December 31, 2017 , $3.7 billion and $5.3 billion , respectively, of our Agency repurchase agreements matured overnight and none of our repurchase agreements were due on demand." id="sjs-B4">Repurchase Agreements and Other Secured Borrowings We pledge our securities as collateral under our borrowing agreements with financial institutions. Interest rates on our 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, 2018 , we had met all margin call requirements. For additional information regarding our pledged assets, please refer to Note 7 . Repurchase Agreements As of March 31, 2018 and December 31, 2017 , we had $49.0 billion and $50.3 billion , respectively, of repurchase agreements outstanding. The terms and conditions of our repurchase agreements are typically negotiated on a transaction-by-transaction basis. Our repurchase agreements with original maturities greater than one year have floating interest rates based on an index plus or minus a fixed spread. The following table summarizes our borrowings under repurchase agreements by their remaining maturities as of March 31, 2018 and December 31, 2017 (dollars in millions): March 31, 2018 December 31, 2017 Remaining Maturity Repurchase Agreements Weighted Average Interest Rate Weighted Average Days to Maturity Repurchase Agreements Weighted Average Interest Rate Weighted Average Days to Maturity Agency repo: ≤ 1 month $ 24,939 1.79 % 14 $ 19,771 1.59 % 11 > 1 to ≤ 3 months 12,881 1.70 % 57 16,150 1.50 % 50 > 3 to ≤ 6 months 3,381 1.76 % 134 7,287 1.50 % 130 > 6 to ≤ 9 months 485 2.07 % 214 2,361 1.66 % 225 > 9 to ≤ 12 months 3,678 1.96 % 297 202 1.64 % 297 > 12 to ≤ 24 months 2,267 2.29 % 596 1,700 1.84 % 468 > 24 to ≤ 36 months 1,325 2.26 % 937 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 48,956 1.82 % 109 $ 50,296 1.57 % 116 As of March 31, 2018 and December 31, 2017 , $3.7 billion and $5.3 billion , respectively, of our Agency repurchase agreements matured overnight and none of our repurchase agreements were due on demand.

Derivative and Other Hedging In

Derivative and Other Hedging Instruments	3 Months Ended
	Mar. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
US Government Futures Securities [Table Text Block]	U.S. Treasury Futures March 31, 2018 December 31, 2017 Maturity Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 5 years $ (730 ) $ (831 ) $ (836 ) $ (5 ) $ (730 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,974 ) (1,999 ) (25 ) (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (2,380 ) $ (2,805 ) $ (2,835 ) $ (30 ) $ (2,910 ) $ (3,570 ) $ (3,551 ) $ 19 ________________________________ 1. Net carrying value represents the difference between the fair market value and the cost basis (or the forward price to be paid/(received) for the underlying U.S. Treasury security) of the U.S. Treasury futures contract as of period-end and is reported in derivative assets/(liabilities), at fair value in our consolidated balance sheets.
Derivative and Other Hedging Instruments	Derivative and Other Hedging Instruments We hedge a portion of our interest rate risk by entering into interest rate swaps, interest rate swaptions and U.S. Treasury securities and U.S. Treasury futures contracts, primarily through short sales. We may also utilize TBA securities, options and other types of derivative instruments to hedge a portion of our risk. 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 . 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/(liabilities) as of March 31, 2018 and December 31, 2017 (in millions): Derivative and Other Hedging Instruments Balance Sheet Location March 31, 2018 December 31, 2017 Interest rate swaps Derivative assets, at fair value $ 174 $ 81 Swaptions Derivative assets, at fair value 153 75 TBA securities Derivative assets, at fair value 83 30 U.S. Treasury futures - short Derivative assets, at fair value — 19 Total derivative assets, at fair value $ 410 $ 205 Interest rate swaps Derivative liabilities, at fair value $ (1 ) $ (1 ) TBA securities Derivative liabilities, at fair value (1 ) (27 ) U.S. Treasury futures - short Derivative liabilities, at fair value (30 ) — Total derivative liabilities, at fair value $ (32 ) $ (28 ) U.S. Treasury securities - long U.S. Treasury securities, at fair value $ 224 $ — U.S. Treasury securities - short Obligation to return securities borrowed under reverse repurchase agreements, at fair value (10,352 ) (10,467 ) Total U.S. Treasury securities, net at fair value $ (10,128 ) $ (10,467 ) The following tables summarize certain characteristics of our derivative and other hedging instruments outstanding as of March 31, 2018 and December 31, 2017 (dollars in millions): March 31, 2018 December 31, 2017 Interest Rate Swaps Notional 1 Average Rate 2 Average Average Notional 1 Average Rate 2 Average Average ≤ 3 years $ 21,075 1.51% 1.90% 1.5 $ 21,025 1.40% 1.46% 1.5 > 3 to ≤ 5 years 8,375 1.84% 1.87% 4.1 6,825 1.82% 1.43% 4.1 > 5 to ≤ 7 years 5,075 2.16% 1.96% 6.0 5,775 2.02% 1.44% 5.9 > 7 to ≤ 10 years 7,550 2.17% 1.88% 8.9 6,650 2.10% 1.42% 9.1 > 10 years 3,175 2.49% 1.91% 12.9 3,425 2.49% 1.45% 12.9 Total $ 45,250 1.82% 1.90% 4.5 $ 43,700 1.74% 1.44% 4.5 ________________________________ 1. As of March 31, 2018 and December 31, 2017 , notional amount includes forward starting swaps of $2.5 billion and $4.6 billion , respectively, with an average forward start date of 0.4 and 0.3 years, respectively. 2. Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.77% and 1.68% as of March 31, 2018 and December 31, 2017 , respectively. Swaptions Option Underlying Payer Swap Current Option Expiration Date Cost Basis Fair Value Average Months to Current Option Expiration Date 1 Notional Amount Average Fixed Pay Rate Average Receive Rate (LIBOR) Average Term (Years) March 31, 2018 ≤ 1 year $ 110 $ 104 7 $ 5,050 2.74% 3M 8.0 > 1 year ≤ 2 years 24 29 16 1,200 2.83% 3M 8.1 > 2 year ≤ 3 years 18 20 27 500 2.78% 3M 10.0 Total $ 152 $ 153 10 $ 6,750 2.76% 3M 8.2 December 31, 2017 ≤ 1 year $ 118 $ 46 7 $ 5,100 2.71% 3M 8.8 > 1 year ≤ 2 years 23 16 18 1,050 2.71% 3M 8.7 > 2 year ≤ 3 years 18 13 30 500 2.78% 3M 10.0 Total $ 159 $ 75 10 $ 6,650 2.72% 3M 8.9 ________________________________ 1. As of March 31, 2018 and December 31, 2017 , ≤ 1 year notional amount includes $700 million of Bermudan swaptions where the options may be exercised on predetermined dates up to their final exercise date, which is six months prior to the underlying swaps' maturity date. U.S. Treasury Securities March 31, 2018 December 31, 2017 Maturity Face Amount Net Long / (Short) Cost Basis Fair Value Face Amount Net Long / (Short) Cost Basis Fair Value 5 years $ 50 $ 50 $ 54 $ (288 ) $ (286 ) $ (283 ) 7 years (6,451 ) (6,419 ) (6,235 ) (6,131 ) (6,106 ) (6,029 ) 10 years (4,172 ) (4,122 ) (3,947 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities, net $ (10,573 ) $ (10,491 ) $ (10,128 ) $ (10,699 ) $ (10,622 ) $ (10,467 ) U.S. Treasury Futures March 31, 2018 December 31, 2017 Maturity Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 5 years $ (730 ) $ (831 ) $ (836 ) $ (5 ) $ (730 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,974 ) (1,999 ) (25 ) (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (2,380 ) $ (2,805 ) $ (2,835 ) $ (30 ) $ (2,910 ) $ (3,570 ) $ (3,551 ) $ 19 ________________________________ 1. Net carrying value represents the difference between the fair market value and the cost basis (or the forward price to be paid/(received) for the underlying U.S. Treasury security) of the U.S. Treasury futures contract as of period-end and is reported in derivative assets/(liabilities), at fair value in our consolidated balance sheets. March 31, 2018 December 31, 2017 TBA Securities by Coupon Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 15-Year TBA securities: 2.5% $ 403 $ 390 $ 394 $ 4 $ 1,373 $ 1,372 $ 1,370 $ (2 ) 3.0% 2,774 2,756 2,768 12 3,161 3,225 3,217 (8 ) 3.5% 750 761 764 3 414 428 428 — Total 15-Year TBA securities 3,927 3,907 3,926 19 4,948 5,025 5,015 (10 ) 30-Year TBA securities: 3.0% 3,822 3,690 3,726 36 4,317 4,303 4,312 9 3.5% 3,272 3,259 3,276 17 3,932 4,027 4,034 7 4.0% 2,650 2,709 2,719 10 2,338 2,449 2,446 (3 ) 4.5% (35 ) (36 ) (36 ) — (61 ) (65 ) (65 ) — Total 30-Year TBA securities, net 9,709 9,622 9,685 63 10,526 10,714 10,727 13 Total TBA securities, net $ 13,636 $ 13,529 $ 13,611 $ 82 $ 15,474 $ 15,739 $ 15,742 $ 3 ________________________________ 1. Net carrying value represents the difference between the fair market value and the cost basis (or the forward price to be paid/(received) for the underlying Agency security) 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 following table summarizes 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, 2018 and 2017 (in millions): Derivative and Other Hedging Instruments Beginning Notional Amount Additions Settlement, Termination, Expiration or Exercise Ending Notional Amount Gain/(Loss) on Derivative Instruments and Other Securities, Net 1 Three months ended March 31, 2018: TBA securities, net $ 15,474 43,669 (45,507 ) $ 13,636 $ (292 ) Interest rate swaps $ 43,700 3,150 (1,600 ) $ 45,250 663 Payer swaptions $ 6,650 1,100 (1,000 ) $ 6,750 91 U.S. Treasury securities - short position $ (10,699 ) (662 ) 563 $ (10,798 ) 212 U.S. Treasury securities - long position $ — 959 (734 ) $ 225 — U.S. Treasury futures contracts - short position $ (2,910 ) (2,909 ) 3,439 $ (2,380 ) 62 $ 736 Three months ended March 31, 2017: TBA securities, net $ 10,916 36,096 (32,842 ) $ 14,170 $ 39 Interest rate swaps $ 37,175 1,300 (2,700 ) $ 35,775 22 Payer swaptions $ 1,200 1,000 — $ 2,200 (11 ) U.S. Treasury securities - short position $ (8,061 ) (2,558 ) 1,450 $ (9,169 ) (78 ) U.S. Treasury securities - long position $ 189 303 (492 ) $ — 1 U.S. Treasury futures contracts - short position $ (1,810 ) (1,810 ) 1,810 $ (1,810 ) (12 ) $ (39 ) ________________________________ 1. Amounts above exclude other miscellaneous gains and losses 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, 2018
Pledged Assets [Abstract]
Pledged Assets	30 and ≤ 60 days 8,001 8,249 24 12,950 13,061 38 > 60 and ≤ 90 days 5,561 5,724 17 4,000 4,013 11 > 90 days 12,205 12,570 36 15,385 15,512 45 Total RMBS $ 50,996 $ 52,482 $ 152 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $174 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of March 31, 2018 and December 31, 2017 , respectively. 2. March 31, 2018 amounts exclude $115 million of repledged U.S. Treasury securities received as collateral from counterparties. The table above excludes Agency securities transferred to our consolidated VIEs. Securities transferred to our consolidated VIEs can only be used to settle the obligations of each respective VIE. However, we may pledge our retained interests in our consolidated VIEs as collateral under our repurchase agreements and derivative contracts. Please refer to Note 4 for additional information regarding our consolidated VIEs. Assets Pledged from Counterparties As of March 31, 2018 and December 31, 2017 , 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, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements 1 Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 10,712 $ — $ 10,712 $ 10,853 $ — $ 10,853 Cash — 247 247 — 82 82 Total $ 10,712 $ 247 $ 10,959 $ 10,853 $ 82 $ 10,935 U.S Treasury securities received as collateral under our reverse repurchase agreements that we use to cover short sales of U.S. Treasury securities are accounted for as securities borrowing transactions. 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 master netting arrangements and can potentially be offset on our consolidated balance sheets as of March 31, 2018 and December 31, 2017 (in millions): Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Received 2 March 31, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 327 $ — $ 327 $ (1 ) $ (243 ) $ 83 TBA securities, at fair value 83 — 83 (1 ) — 82 Receivable under reverse repurchase agreements 10,770 — 10,770 (7,606 ) (3,164 ) — Total $ 11,180 $ — $ 11,180 $ (7,608 ) $ (3,407 ) $ 165 December 31, 2017 Interest rate swap and swaption agreements, at fair value 1 $ 156 $ — $ 156 $ (1 ) $ (82 ) $ 73 TBA securities, at fair value 30 — 30 (22 ) — 8 Receivable under reverse repurchase agreements 10,961 — 10,961 (9,682 ) (1,279 ) — Total $ 11,147 $ — $ 11,147 $ (9,705 ) $ (1,361 ) $ 81 Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Pledged 2 March 31, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 1 — 1 (1 ) — — Repurchase agreements 48,956 — 48,956 (7,606 ) (41,350 ) — Total $ 48,958 $ — $ 48,958 $ (7,608 ) $ (41,350 ) $ — December 31, 2017 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 27 — 27 (22 ) (5 ) — Repurchase agreements and FHLB advances 50,296 — 50,296 (9,682 ) (40,614 ) — Total $ 50,324 $ — $ 50,324 $ (9,705 ) $ (40,619 ) $ — ________________________________ 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 pledged / received 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." id="sjs-B4">Pledged Assets Our funding agreements 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. Our derivative contracts similarly require us to fully collateralize our obligations under such agreements, which will vary over time based on similar factors as well as our counterparties' determination of the value of the derivative contract. We are typically required to post initial margin upon execution of derivative transactions, such as under our interest rate swap agreements and TBA contracts, and subsequently post or receive variation margin based on daily fluctuations in fair value. Our prime brokerage agreements, pursuant to which we receive custody and settlement services, and the clearing organizations utilized by our wholly-owned captive broker-dealer subsidiary, Bethesda Securities, LLC, also require that we post minimum daily clearing deposits. If we breach our collateral requirements, we will be required to fully settle our obligations under the agreements, which could include a forced liquidation of our pledged collateral. Our 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, our funding agreements and derivative contracts expose us to credit risk relating to potential losses that could be recognized if our counterparties fail to perform their obligations under such agreements. We minimize this risk by limiting our counterparties to major financial institutions with acceptable credit ratings or to registered clearinghouses and U.S. government agencies, 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, clearinghouse guarantee funds and other resources that are available in the event of a clearing member default. Our International Swaps and Derivatives Association ("ISDA") Master Agreements contain a cross default provision under which a default under the terms of certain of our other indebtedness in excess of certain thresholds causes an event of default under the ISDA Master 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 up to certain specified levels. As of March 31, 2018 , 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, 2018 , our amount at risk with any counterparty related to our repurchase agreements was less than 5% of our tangible stockholders' equity and our maximum 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 funding, derivative and prime broker agreements by type, including securities pledged related to securities sold but not yet settled, as of March 31, 2018 and December 31, 2017 (in millions): March 31, 2018 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 50,996 $ 621 $ 202 $ 410 $ 52,229 U.S. Treasury securities - fair value 3 115 — 49 — 164 Accrued interest on pledged securities 151 2 1 1 155 Restricted cash and cash equivalents 49 — 331 6 386 Total $ 51,311 $ 623 $ 583 $ 417 $ 52,934 December 31, 2017 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 52,497 $ 662 $ 221 $ 519 $ 53,899 U.S. Treasury securities - fair value 3 113 — 72 — 185 Accrued interest on pledged securities 153 2 1 2 158 Restricted cash and cash equivalents 35 — 281 1 317 Total $ 52,798 $ 664 $ 575 $ 522 $ 54,559 ________________________________ 1. Includes $174 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of March 31, 2018 and December 31, 2017 , respectively. 2. Includes margin for TBAs cleared through prime brokers and other clearing deposits. 3. Includes repledged securities received as collateral from counterparties. The following table summarizes our securities pledged as collateral under our repurchase agreements by the remaining maturity of our borrowings, including securities pledged related to sold but not yet settled securities, as of March 31, 2018 and December 31, 2017 (in millions). For the corresponding borrowings associated with the following amounts and the interest rates thereon, refer to Note 5 . March 31, 2018 December 31, 2017 Securities Pledged by Remaining Maturity of Repurchase Agreements Fair Value of Pledged Securities Amortized Cost of Pledged Securities Accrued Interest on Pledged Securities Fair Value of Pledged Securities Amortized Cost of Pledged Securities Accrued Interest on Pledged Securities RMBS: 1,2 ≤ 30 days $ 25,229 $ 25,939 $ 75 $ 20,162 $ 20,313 $ 59 > 30 and ≤ 60 days 8,001 8,249 24 12,950 13,061 38 > 60 and ≤ 90 days 5,561 5,724 17 4,000 4,013 11 > 90 days 12,205 12,570 36 15,385 15,512 45 Total RMBS $ 50,996 $ 52,482 $ 152 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $174 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of March 31, 2018 and December 31, 2017 , respectively. 2. March 31, 2018 amounts exclude $115 million of repledged U.S. Treasury securities received as collateral from counterparties. The table above excludes Agency securities transferred to our consolidated VIEs. Securities transferred to our consolidated VIEs can only be used to settle the obligations of each respective VIE. However, we may pledge our retained interests in our consolidated VIEs as collateral under our repurchase agreements and derivative contracts. Please refer to Note 4 for additional information regarding our consolidated VIEs. Assets Pledged from Counterparties As of March 31, 2018 and December 31, 2017 , 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, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements 1 Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 10,712 $ — $ 10,712 $ 10,853 $ — $ 10,853 Cash — 247 247 — 82 82 Total $ 10,712 $ 247 $ 10,959 $ 10,853 $ 82 $ 10,935 U.S Treasury securities received as collateral under our reverse repurchase agreements that we use to cover short sales of U.S. Treasury securities are accounted for as securities borrowing transactions. 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 master netting arrangements and can potentially be offset on our consolidated balance sheets as of March 31, 2018 and December 31, 2017 (in millions): Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Received 2 March 31, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 327 $ — $ 327 $ (1 ) $ (243 ) $ 83 TBA securities, at fair value 83 — 83 (1 ) — 82 Receivable under reverse repurchase agreements 10,770 — 10,770 (7,606 ) (3,164 ) — Total $ 11,180 $ — $ 11,180 $ (7,608 ) $ (3,407 ) $ 165 December 31, 2017 Interest rate swap and swaption agreements, at fair value 1 $ 156 $ — $ 156 $ (1 ) $ (82 ) $ 73 TBA securities, at fair value 30 — 30 (22 ) — 8 Receivable under reverse repurchase agreements 10,961 — 10,961 (9,682 ) (1,279 ) — Total $ 11,147 $ — $ 11,147 $ (9,705 ) $ (1,361 ) $ 81 Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Pledged 2 March 31, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 1 — 1 (1 ) — — Repurchase agreements 48,956 — 48,956 (7,606 ) (41,350 ) — Total $ 48,958 $ — $ 48,958 $ (7,608 ) $ (41,350 ) $ — December 31, 2017 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 27 — 27 (22 ) (5 ) — Repurchase agreements and FHLB advances 50,296 — 50,296 (9,682 ) (40,614 ) — Total $ 50,324 $ — $ 50,324 $ (9,705 ) $ (40,619 ) $ — ________________________________ 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 pledged / received 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, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurements We determine the fair value of our financial instruments based on our estimate of the price that would be received to sell the asset or paid to transfer the liability in an orderly transaction between market participants at the measurement date. We typically obtain price estimates from multiple third-party pricing services and dealers or, if applicable, the clearing exchange (see Note 3 for further details.) We utilize a three-level valuation hierarchy for disclosure of fair value measurements. 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. The three levels of valuation 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 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 loss severities, 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. We also review third-party price estimates and perform procedures to validate their reasonableness, including an analysis of the range of estimates for each position, comparison to recent trade activity for similar securities, and for consistency with market conditions observed as of the measurement date. While we do not adjust prices we obtain from pricing sources, we will exclude prices for securities from our estimation of fair value if we determine (based on our validation procedures and our market knowledge and expertise) that the price is significantly different from what 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 categorization. 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, 2018 and December 31, 2017 based on their categorization within the valuation hierarchy (in millions). There were no transfers between valuation hierarchy levels during the periods presented. March 31, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Agency securities $ — $ 54,141 $ — $ — $ 55,506 $ — Agency securities transferred to consolidated VIEs — 621 — — 662 — Credit risk transfer securities — 884 — — 876 — Non-Agency securities — 36 — — 36 — U.S. Treasury securities 224 — — — — — REIT equity securities 42 — — 29 — — Interest rate swaps — 174 — — 81 — Swaptions — 153 — — 75 — TBA securities — 83 — — 30 — U.S. Treasury futures — — — 19 — — Total $ 266 $ 56,092 $ — $ 48 $ 57,266 $ — Liabilities: Debt of consolidated VIEs $ — $ 336 $ — $ — $ 357 $ — Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements 10,352 — — 10,467 — — Interest rate swaps — 1 — — 1 — TBA securities — 1 — — 27 — U.S. Treasury futures 30 — — — — — Total $ 10,352 $ 338 $ — $ 10,467 $ 385 $ — Excluded from the table above are financial instruments, including cash and cash equivalents, restricted cash and cash equivalents, receivables, payables and borrowings under repurchase agreements, which are presented in our consolidated financial statements at cost. The cost basis of these instruments is determined to approximate fair value due to their short duration or, in the case of longer-term repo, due to floating rates of interest based on an index plus or minus a fixed spread which is consistent with fixed spreads demanded in the market. We estimate the fair value of these instruments using "Level 1" or "Level 2" inputs.

Net Income (Loss) Per Common Sh

Net Income (Loss) Per Common Share (Notes)	3 Months Ended
	Mar. 31, 2018
Net Income (Loss) Per Common Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	Three Months Ended March 31, 2018 2017 Weighted average number of common shares outstanding - basic 391.3 331.0 Unvested restricted stock units and performance share units 0.2 0.1 Weighted average number of common shares outstanding - diluted 391.5 331.1 Net income available to common stockholders $ 415 $ 69 Net income per common share - basic and diluted $ 1.06 $ 0.21
Earnings Per Share [Text Block]	Net Income Per Common Share Basic net income per common share includes no dilution and is computed by dividing net income applicable to common stock by the weighted-average number of common shares outstanding for the respective period. Diluted earnings per common share includes the impact of dilutive potential common shares outstanding during the period using the treasury stock method. Dilutive potential common shares outstanding include unvested restricted stock units and performance share units granted under our long-term incentive program to employees and non-employee Board of Directors. The following table presents the computations of basic and diluted net income per common share for the periods indicated (shares and dollars in millions): Three Months Ended March 31, 2018 2017 Weighted average number of common shares outstanding - basic 391.3 331.0 Unvested restricted stock units and performance share units 0.2 0.1 Weighted average number of common shares outstanding - diluted 391.5 331.1 Net income available to common stockholders $ 415 $ 69 Net income per common share - basic and diluted $ 1.06 $ 0.21

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
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. As of December 31, 2017 and March 31, 2018, 8,050 shares were designated as 7.750% Series B Cumulative Redeemable Preferred Stock ("Series B Preferred Stock") and 13,800 shares were designated as 7.00% Series C Fixed-to-Floating Rate Cumulative Redeemable Preferred Stock ("Series C Preferred Stock"). Shares of Series B and Series C Preferred Stock are represented by depositary shares equal to 1/1000 interest in each share of Series B and Series C Preferred Stock, respectively. As of December 31, 2017 and March 31, 2018 , we had 7,000 shares of Series B Preferred Stock and 13,000 shares of Series C Preferred Stock outstanding (represented by 7.0 million Series B depositary shares and 13.0 million Series C depositary shares outstanding, respectively) and 9,980,000 of authorized but unissued shares of preferred stock. Holders of depository shares underlying our Series B Preferred Stock are entitled to receive cumulative cash dividends at a rate of 7.750% per annum of their $25.00 per depositary share liquidation preference. Holders of depositary shares underlying our Series C Preferred Stock are entitled to receive cumulative cash dividends at a rate of 7.00% per annum up to, and including, October 14, 2022 and thereafter at a floating rate equal to three-month LIBOR plus a spread of 5.111% per annum of their $25.00 per depositary share liquidation preference. Dividends are payable quarterly in arrears on the 15th day of each January, April, July and October. As of March 31, 2018 , we had declared all required quarterly dividends on our preferred stock. Our preferred stock ranks senior to our common stock with respect to the payment of dividends and the distribution of assets upon a voluntary or involuntary liquidation, dissolution or winding up of the Company. Our preferred stock has no stated maturity, is not subject to any sinking fund or mandatory redemption and ranks on parity with each other. Under certain circumstances upon a change of control, our preferred stock is convertible to shares of our common stock. Holders of our preferred stock and depository shares underlying our preferred stock have no voting rights, except under limited conditions. Beginning on May 8, 2019 and October 15, 2022, depository shares underlying our Series B and Series C Preferred Stock, respectively, will be redeemable at $25.00 per depositary share, plus accumulated and unpaid dividends (whether or not declared) exclusively at our option. We may redeem shares of our preferred stock prior to our optional redemption date under certain circumstances intended to preserve our qualification as a REIT for Federal income tax purposes. Preferred Stock Offering and Redemption In August 2017, we issued 13,000 shares of Series C Preferred Stock in a public offering of 13.0 million Series C depositary shares at a price of $25 per depositary share for net proceeds of $315 million , after deducting underwriting discounts and estimated offering expenses. In September 2017, we redeemed all of our issued and outstanding shares of 8.000% Series A Cumulative Redeemable Preferred Stock ("Series A Preferred Stock") for $173 million (or $25 per share liquidation preference), plus accrued and unpaid dividends, and, in October of 2017, we filed a Certificate of Elimination of our Series A Preferred Stock with the Secretary of State of the State of Delaware, which eliminated the designation of Series A Preferred Stock from our amended and restated certificate of incorporation. Common Stock Offerings In May 2017, we completed a public offering in which 24.5 million shares of our common stock were sold to the underwriters for proceeds of $503 million , or $20.51 per common share, net of offering costs. In September 2017, we completed a public offering in which 28.2 million shares of our common stock were sold to the underwriters for proceeds of $577 million , or $20.47 per common share, net of estimated offering costs. At-the-Market Offering Program In February 2017, we entered into agreements with sales agents to publicly offer and sell shares of our common stock in privately negotiated and/or at-the-market transactions from time-to-time up to an aggregate amount of $750 million of shares of our common stock. During fiscal year 2017, we sold 7.6 million shares of our common stock under the sales agreements for proceeds of $159 million , or $20.96 per common share, net of estimated offering costs. As of March 31, 2018 , $589 million of shares of our common stock remain available for issuance under this program. Accumulated Other Comprehensive Income (Loss) The following table summarizes changes to accumulated OCI for the three months ended March 31, 2018 and 2017 (in millions): Three Months Ended March 31, Accumulated Other Comprehensive Income (Loss) 2018 2017 Beginning Balance $ (345 ) $ (397 ) OCI before reclassifications (620 ) (38 ) (Gain) loss amounts for available-for-sale securities reclassified from accumulated OCI to realized gain (loss) on sale of investment securities (1 ) 84 Ending Balance $ (966 ) $ (351 )

Subsequent Event

Subsequent Event	3 Months Ended
	Mar. 31, 2018
Subsequent Events [Abstract]
Subsequent Event	Subsequent Events On April 12, 2018 , our Board of Directors declared a monthly dividend of $0.18 per common share, payable on May 9, 2018 to common stockholders of record as of April 30, 2018 , respectively. On May 2, 2018, we entered into an amendment to our management agreement with MTGE in connection with the proposed acquisition of MTGE by Annaly Capital Management, Inc. The transaction is expected to close in the third quarter of 2018, subject to customary closing conditions. Pursuant to the amendment, we will continue to manage MTGE through the closing of the merger and for a short transitional period following the merger. In addition to regular monthly management fees payable for ongoing service through the transition period, under the amendment we will be paid a termination fee of $41.7 million.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Policy)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reverse Repurchase Agreements Policy [Policy Text Block]	Reverse Repurchase Agreements and Obligation to Return Securities Borrowed under Reverse Repurchase Agreements We borrow securities to cover short sales of U.S. Treasury securities through reverse repurchase transactions under our master repurchase agreements (see Derivative Instruments below). 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. Our reverse repurchase agreements typically have maturities of 30 days or less. The fair value of our reverse repurchase agreements is assumed to equal cost as the interest rates generally reset daily.
New Accounting Pronouncements, Policy [Policy Text Block]	Recent Accounting Pronouncements We consider the applicability and impact of all Accounting Standards Updates ("ASUs") issued by the Financial Accounting Standards Board. ASUs not listed below were determined to be either not applicable, are not expected to have a significant impact on our consolidated financial statements when adopted, or did not have a significant impact on our consolidated financial statements upon adoption. ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): ASU 2016-13 changes the impairment model for most financial assets and certain other instruments. Allowances for credit losses on available-for-sale debt securities will be recognized, rather than direct reductions in the amortized cost of the investments. The new model also requires the estimation of lifetime expected credit losses and corresponding recognition of allowance for losses on trade and other receivables, held-to-maturity debt securities, loans, and other instruments held at amortized cost. The ASU requires certain recurring disclosures and is effective for annual periods, and interim periods within those annual periods, beginning on or after December 15, 2019, with early adoption permitted for annual periods, and interim periods within those annual periods, beginning on or after December 15, 2018. ASU 2016-13 is not expected to have a significant impact on our consolidated financial statements.
Investment Securities	Investment Securities Agency RMBS consist of residential mortgage pass-through securities and collateralized mortgage obligations ("CMOs") guaranteed by the Federal National Mortgage Association ("Fannie Mae"), Federal Home Loan Mortgage Corporation ("Freddie Mac," and together with Fannie Mae, the "GSEs") or the Government National Mortgage Association ("Ginnie Mae"). CRT securities are risk sharing instruments issued by the GSEs, and similarly structured transactions issued by third-party market participants, that transfer a portion of the risk associated with credit losses within pools of conventional residential mortgage loans from the GSEs and/or third parties to private investors. Unlike Agency RMBS, full repayment of the original principal balance of CRT securities is not guaranteed by a GSE or U.S. Government agency; rather, "credit risk transfer" is achieved by writing down the outstanding principal balance of the CRT securities if credit losses on a related pool of loans exceed certain thresholds. By reducing the amount that they are obligated to repay to holders of CRT securities, the GSEs and/or other third parties offset credit losses on the related loans. Non-Agency RMBS and CMBS (together, "Non-Agency MBS") are backed by residential and commercial mortgage loans, respectively, packaged and securitized by a private institution, such as a commercial bank. Non-Agency MBS typically benefit from credit enhancements derived from structural elements, such as subordination, overcollateralization or insurance, but nonetheless carry a higher level of credit exposure than Agency RMBS. Mortgage-related securities may also include investments in the common stock of other publicly traded mortgage REITs, including MTGE, that primarily invest in Agency securities, non-Agency securities, other mortgage related instruments and/or real estate on a leveraged basis. As of March 31, 2018 , our investments in REIT equity securities consisted solely of MTGE common stock. Accounting Standards Codification ("ASC") Topic 320, Investments—Debt and Equity Securities , 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. Alternatively, we may elect the fair value option of accounting for such securities pursuant to ASC Topic 825, Financial Instruments . All of our securities are reported at fair value as they have either been designated as available-for-sale or trading or we have elected the fair value option of accounting. Unrealized gains and losses on securities classified as available-for-sale are reported in accumulated other comprehensive income ("OCI"). Unrealized gains and losses on securities classified as trading or for which we elected the fair value option are reported in net income through other gain (loss) during the period in which they occur. Upon the sale of a security designated as available-for-sale, 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. Prior to fiscal year 2017, we primarily designated our investment securities as available-for-sale. On January 1, 2017, we began electing the fair value option of accounting for all investment securities acquired after fiscal year 2016. In our view, this election simplifies the accounting for investment securities and more appropriately reflects the results of our operations for a particular reporting period, as the fair value changes for these assets are presented in a manner consistent with the presentation and timing of the fair value changes of our hedging instruments. We are not permitted to change the designation of securities acquired prior to January 1, 2017; accordingly, such securities will continue to be classified as available-for-sale securities until we receive full repayment of principal or we dispose of the security. We estimate the fair value of our investment securities based on prices provided by multiple third-party pricing services and non-binding dealer quotes (collectively "pricing sources"). These pricing sources use various valuation approaches, including market and income approaches, using "Level 2" inputs. The pricing sources primarily utilize a matrix pricing technique that interpolates the estimated fair value of our Agency RMBS based on observed quoted prices for forward contracts in the Agency RMBS "to-be-announced" market ("TBA securities") of the same coupon, maturity and issuer, adjusted to reflect the specific characteristics of the pool of mortgages underlying the Agency security, which may include maximum loan balance, loan vintage, loan-to-value ratio, geography and other characteristics as may be appropriate. The pricing sources may also utilize discounted cash flow model-derived pricing techniques to estimate the fair value of investment securities. Such models incorporate market-based discount rate assumptions based on observable inputs such as recent trading activity, credit data, volatility statistics, benchmark interest rate curves and other market data that are current as of the measurement date and may include certain unobservable inputs, such as assumptions of future levels of prepayment, defaults and loss severities. We review the pricing estimates obtained from the pricing sources and perform procedures to validate their reasonableness. Refer to Note 8 for further discussion of fair value measurements. We evaluate our investments designated as available-for-sale 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 Agency RMBS and non-Agency MBS of high credit quality 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 . We estimate long-term prepayment speeds of our mortgage securities using a third-party service and market data. The third-party service provider estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates, mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, interest rate 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 third-party estimates and, based on our judgment, we may adjust the estimates. We review our actual and anticipated prepayment experience on at least a quarterly basis and effective yields are recalculated when differences arise between (i) our previously estimated future prepayments and (ii) actual prepayments to date and our current estimated future prepayments. If the actual and estimated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. At the time we purchase CRT securities and non-Agency MBS that are not of high credit quality, we determine an effective yield based on our estimate of the timing and amount of future cash flows and our cost basis. Our initial cash flow estimates for these investments are based on our observations of current information and events and include assumptions related to interest rates, prepayment rates and the impact of default and severity rates on the timing and amount of credit losses. On at least a quarterly basis, we review the estimated cash flows and make appropriate adjustments, based on inputs and analysis received from external sources, internal models, and our judgment regarding such inputs and other factors. Any resulting changes in effective yield are recognized prospectively based on the current amortized cost of the investment as adjusted for credit impairment, if any.
Repurchase and Resale Agreements Policy [Policy Text Block]	Repurchase Agreements We finance the acquisition of securities for our investment portfolio primarily through repurchase transactions under master repurchase agreements. Pursuant to ASC Topic 860, Transfers and Servicing , we account for repurchase transactions as collateralized financing transactions, which are carried at their contractual amounts (cost), plus accrued interest. Our repurchase agreements typically have maturities of less than one year, but may extend up to five years or more. Interest rates on our repurchase agreements generally correspond to one or three-month LIBOR plus or minus a fixed spread. The fair value of our repurchase agreements is assumed to equal cost as the interest rates are considered to be at market.
Derivative Instruments	Derivative Instruments We use a variety of derivative instruments to hedge a portion of our exposure to market risks, including interest rate, prepayment, extension and liquidity risks. 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 primary instruments that we use are interest rate swaps, options to enter into interest rate swaps ("swaptions"), U.S. Treasury securities and U.S. Treasury futures contracts. We also use forward contracts in the Agency RMBS "to-be-announced" market, or TBA securities, to invest in and finance Agency securities as well as to periodically reduce our exposure to Agency RMBS. 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 our accompanying consolidated balance sheets 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 if the counterparties to these instruments fail to perform their obligations under the contracts. Our derivative agreements require that we post or receive collateral to mitigate such risk. We also attempt to minimize our risk of loss by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to hedge the variable cash flows associated with our borrowings made under repurchase agreements. Under our interest rate swap agreements, we typically pay a fixed rate and receive a floating rate based on one or three-month LIBOR ("payer swaps") with terms up to 20 years. Our swap agreements are privately negotiated in the over-the-counter ("OTC") market. The majority of our interest rate swaps are centrally cleared through a registered commodities exchange. We value centrally cleared interest rate swaps using the daily settlement price, or fair value, determined by the clearing exchange based on a pricing model that references observable market inputs, including LIBOR, swap rates and the forward yield curve. Our centrally cleared swaps require that we post an "initial margin" amount determined by the clearing exchange, which is generally intended to be set at a level sufficient to protect the exchange from the interest rate swap's maximum estimated single-day price movement. We also exchange daily settlements of "variation margin" based upon changes in fair value, as measured by the exchange. Pursuant to rules governing central clearing activities, we recognize variation margin settlements as a direct reduction of the carrying value of the interest rate swap asset or liability. We value non-centrally cleared swaps using a combination of third-party valuations obtained from pricing services and the swap counterparty. The third-party valuations are model-driven using observable inputs, including LIBOR, swap rates and the forward yield curve. We also consider both our own and our counterparties' nonperformance risk in estimating the fair value of our interest rate swaps. In considering the effect of nonperformance risk, we assess the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We purchase interest rate swaptions to help mitigate the potential impact of larger, 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 ("payer swaptions"). We may also enter into swaption agreements that provide us the option to enter into a receive-fixed interest rate swap ("receiver swaptions"). Our interest rate swaption agreements are privately negotiated in the OTC market and are not subject to central clearing. The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. We estimate the fair value of interest rate swaptions using a combination of inputs from counterparty and third-party pricing models based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option, adjusted for non-performance risk, if any. The difference between the premium paid 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. TBA securities A TBA security is a forward contract for the purchase or sale of Agency RMBS at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific Agency RMBS to be delivered into the contract are not known until shortly before the settlement date. We may choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting TBA position, net settling the offsetting positions for cash, and simultaneously purchasing or selling a similar TBA contract for a later settlement date (together referred to as a "dollar roll transaction"). The Agency securities purchased or sold for a forward settlement date are typically priced at a discount to equivalent securities settling in the current month. This difference, or "price drop," is the economic equivalent to interest income on the underlying Agency securities, less an implied funding cost, over the forward settlement period (referred to as "dollar roll income"). Consequently, forward purchases of Agency securities and dollar roll transactions represent a form of off-balance sheet financing. We account for 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 physically settle the TBA contract on the settlement date. We account for TBA dollar roll transactions as a series of derivative transactions. Gains, losses and dollar roll income associated with our TBA contracts are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. We estimate the fair value of TBA securities based on similar methods used to value our Agency RMBS securities. U.S. Treasury securities We purchase and 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 our accompanying consolidated balance sheets 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.
Contingencies Disclosure [Text Block]	Loss Contingencies We evaluate the existence of any pending or threatened litigation or other potential claims against the Company in accordance with ASC Topic 450, Contingencies, which requires that we assess the likelihood and range of potential outcomes of any such matters. We are the defendant in three stockholder derivative lawsuits alleging that certain of our current and former directors and officers breached fiduciary duties and wasted corporate assets relating to past renewals of the management agreement with our former external manager and the internalization of our management, which occurred on July 1, 2016. Although the outcomes of these cases cannot be predicted with certainty, we do not believe that these cases have merit or will result in a material liability, and, as of March 31, 2018 , we did not accrue a loss contingency related to these matters.

Summary of Significant Accoun19

Summary of Significant Accounting Policies Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Derivatives, Policy [Policy Text Block]	Derivative Instruments We use a variety of derivative instruments to hedge a portion of our exposure to market risks, including interest rate, prepayment, extension and liquidity risks. 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 primary instruments that we use are interest rate swaps, options to enter into interest rate swaps ("swaptions"), U.S. Treasury securities and U.S. Treasury futures contracts. We also use forward contracts in the Agency RMBS "to-be-announced" market, or TBA securities, to invest in and finance Agency securities as well as to periodically reduce our exposure to Agency RMBS. 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 our accompanying consolidated balance sheets 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 if the counterparties to these instruments fail to perform their obligations under the contracts. Our derivative agreements require that we post or receive collateral to mitigate such risk. We also attempt to minimize our risk of loss by limiting our counterparties to major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to hedge the variable cash flows associated with our borrowings made under repurchase agreements. Under our interest rate swap agreements, we typically pay a fixed rate and receive a floating rate based on one or three-month LIBOR ("payer swaps") with terms up to 20 years. Our swap agreements are privately negotiated in the over-the-counter ("OTC") market. The majority of our interest rate swaps are centrally cleared through a registered commodities exchange. We value centrally cleared interest rate swaps using the daily settlement price, or fair value, determined by the clearing exchange based on a pricing model that references observable market inputs, including LIBOR, swap rates and the forward yield curve. Our centrally cleared swaps require that we post an "initial margin" amount determined by the clearing exchange, which is generally intended to be set at a level sufficient to protect the exchange from the interest rate swap's maximum estimated single-day price movement. We also exchange daily settlements of "variation margin" based upon changes in fair value, as measured by the exchange. Pursuant to rules governing central clearing activities, we recognize variation margin settlements as a direct reduction of the carrying value of the interest rate swap asset or liability. We value non-centrally cleared swaps using a combination of third-party valuations obtained from pricing services and the swap counterparty. The third-party valuations are model-driven using observable inputs, including LIBOR, swap rates and the forward yield curve. We also consider both our own and our counterparties' nonperformance risk in estimating the fair value of our interest rate swaps. In considering the effect of nonperformance risk, we assess the impact of netting and credit enhancements, such as collateral postings and guarantees, and have concluded that our own and our counterparty risk is not significant to the overall valuation of these agreements. Interest rate swaptions We purchase interest rate swaptions to help mitigate the potential impact of larger, 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 ("payer swaptions"). We may also enter into swaption agreements that provide us the option to enter into a receive-fixed interest rate swap ("receiver swaptions"). Our interest rate swaption agreements are privately negotiated in the OTC market and are not subject to central clearing. The premium paid for interest rate swaptions is reported as an asset in our consolidated balance sheets. We estimate the fair value of interest rate swaptions using a combination of inputs from counterparty and third-party pricing models based on the fair value of the future interest rate swap that we have the option to enter into as well as the remaining length of time that we have to exercise the option, adjusted for non-performance risk, if any. The difference between the premium paid 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. TBA securities A TBA security is a forward contract for the purchase or sale of Agency RMBS at a predetermined price, face amount, issuer, coupon and stated maturity on an agreed-upon future date. The specific Agency RMBS to be delivered into the contract are not known until shortly before the settlement date. We may choose, prior to settlement, to move the settlement of these securities out to a later date by entering into an offsetting TBA position, net settling the offsetting positions for cash, and simultaneously purchasing or selling a similar TBA contract for a later settlement date (together referred to as a "dollar roll transaction"). The Agency securities purchased or sold for a forward settlement date are typically priced at a discount to equivalent securities settling in the current month. This difference, or "price drop," is the economic equivalent to interest income on the underlying Agency securities, less an implied funding cost, over the forward settlement period (referred to as "dollar roll income"). Consequently, forward purchases of Agency securities and dollar roll transactions represent a form of off-balance sheet financing. We account for 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 physically settle the TBA contract on the settlement date. We account for TBA dollar roll transactions as a series of derivative transactions. Gains, losses and dollar roll income associated with our TBA contracts are recognized in gain (loss) on derivative instruments and other securities, net in our consolidated statements of comprehensive income. We estimate the fair value of TBA securities based on similar methods used to value our Agency RMBS securities. U.S. Treasury securities We purchase and 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 our accompanying consolidated balance sheets 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, Policy [Policy Text Block]	Investment Securities Agency RMBS consist of residential mortgage pass-through securities and collateralized mortgage obligations ("CMOs") guaranteed by the Federal National Mortgage Association ("Fannie Mae"), Federal Home Loan Mortgage Corporation ("Freddie Mac," and together with Fannie Mae, the "GSEs") or the Government National Mortgage Association ("Ginnie Mae"). CRT securities are risk sharing instruments issued by the GSEs, and similarly structured transactions issued by third-party market participants, that transfer a portion of the risk associated with credit losses within pools of conventional residential mortgage loans from the GSEs and/or third parties to private investors. Unlike Agency RMBS, full repayment of the original principal balance of CRT securities is not guaranteed by a GSE or U.S. Government agency; rather, "credit risk transfer" is achieved by writing down the outstanding principal balance of the CRT securities if credit losses on a related pool of loans exceed certain thresholds. By reducing the amount that they are obligated to repay to holders of CRT securities, the GSEs and/or other third parties offset credit losses on the related loans. Non-Agency RMBS and CMBS (together, "Non-Agency MBS") are backed by residential and commercial mortgage loans, respectively, packaged and securitized by a private institution, such as a commercial bank. Non-Agency MBS typically benefit from credit enhancements derived from structural elements, such as subordination, overcollateralization or insurance, but nonetheless carry a higher level of credit exposure than Agency RMBS. Mortgage-related securities may also include investments in the common stock of other publicly traded mortgage REITs, including MTGE, that primarily invest in Agency securities, non-Agency securities, other mortgage related instruments and/or real estate on a leveraged basis. As of March 31, 2018 , our investments in REIT equity securities consisted solely of MTGE common stock. Accounting Standards Codification ("ASC") Topic 320, Investments—Debt and Equity Securities , 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. Alternatively, we may elect the fair value option of accounting for such securities pursuant to ASC Topic 825, Financial Instruments . All of our securities are reported at fair value as they have either been designated as available-for-sale or trading or we have elected the fair value option of accounting. Unrealized gains and losses on securities classified as available-for-sale are reported in accumulated other comprehensive income ("OCI"). Unrealized gains and losses on securities classified as trading or for which we elected the fair value option are reported in net income through other gain (loss) during the period in which they occur. Upon the sale of a security designated as available-for-sale, 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. Prior to fiscal year 2017, we primarily designated our investment securities as available-for-sale. On January 1, 2017, we began electing the fair value option of accounting for all investment securities acquired after fiscal year 2016. In our view, this election simplifies the accounting for investment securities and more appropriately reflects the results of our operations for a particular reporting period, as the fair value changes for these assets are presented in a manner consistent with the presentation and timing of the fair value changes of our hedging instruments. We are not permitted to change the designation of securities acquired prior to January 1, 2017; accordingly, such securities will continue to be classified as available-for-sale securities until we receive full repayment of principal or we dispose of the security. We estimate the fair value of our investment securities based on prices provided by multiple third-party pricing services and non-binding dealer quotes (collectively "pricing sources"). These pricing sources use various valuation approaches, including market and income approaches, using "Level 2" inputs. The pricing sources primarily utilize a matrix pricing technique that interpolates the estimated fair value of our Agency RMBS based on observed quoted prices for forward contracts in the Agency RMBS "to-be-announced" market ("TBA securities") of the same coupon, maturity and issuer, adjusted to reflect the specific characteristics of the pool of mortgages underlying the Agency security, which may include maximum loan balance, loan vintage, loan-to-value ratio, geography and other characteristics as may be appropriate. The pricing sources may also utilize discounted cash flow model-derived pricing techniques to estimate the fair value of investment securities. Such models incorporate market-based discount rate assumptions based on observable inputs such as recent trading activity, credit data, volatility statistics, benchmark interest rate curves and other market data that are current as of the measurement date and may include certain unobservable inputs, such as assumptions of future levels of prepayment, defaults and loss severities. We review the pricing estimates obtained from the pricing sources and perform procedures to validate their reasonableness. Refer to Note 8 for further discussion of fair value measurements. We evaluate our investments designated as available-for-sale 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 [Policy Text Block]	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 Agency RMBS and non-Agency MBS of high credit quality 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 . We estimate long-term prepayment speeds of our mortgage securities using a third-party service and market data. The third-party service provider estimates prepayment speeds using models that incorporate the forward yield curve, current mortgage rates, mortgage rates of the outstanding loans, age and size of the outstanding loans, loan-to-value ratios, interest rate 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 third-party estimates and, based on our judgment, we may adjust the estimates. We review our actual and anticipated prepayment experience on at least a quarterly basis and effective yields are recalculated when differences arise between (i) our previously estimated future prepayments and (ii) actual prepayments to date and our current estimated future prepayments. If the actual and estimated future prepayment experience differs from our prior estimate of prepayments, we are required to record an adjustment in the current period to the amortization or accretion of premiums and discounts for the cumulative difference in the effective yield through the reporting date. At the time we purchase CRT securities and non-Agency MBS that are not of high credit quality, we determine an effective yield based on our estimate of the timing and amount of future cash flows and our cost basis. Our initial cash flow estimates for these investments are based on our observations of current information and events and include assumptions related to interest rates, prepayment rates and the impact of default and severity rates on the timing and amount of credit losses. On at least a quarterly basis, we review the estimated cash flows and make appropriate adjustments, based on inputs and analysis received from external sources, internal models, and our judgment regarding such inputs and other factors. Any resulting changes in effective yield are recognized prospectively based on the current amortized cost of the investment as adjusted for credit impairment, if any.

Investment Securities (Tables)

Investment Securities (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Securities by Credit Rating [Table Text Block]	As of March 31, 2018 and December 31, 2017 , our investments in CRT and non-Agency securities had the following credit ratings: March 31, 2018 December 31, 2017 CRT and Non-Agency Security Credit Ratings 1 CRT RMBS CMBS CRT RMBS CMBS AAA $ — $ 7 $ — $ — $ 7 $ — BBB 26 — 29 20 — 29 BB 139 — — 136 — — B 698 — — 691 — — Not Rated 21 — — 29 — — Total $ 884 $ 7 $ 29 $ 876 $ 7 $ 29 ________________________________ 1. Represents the lowest of Standard and Poor's ("S&P"), Moody's and Fitch credit ratings, stated in terms of the S&P equivalent rating as of each date.
Available-for-sale Securities [Table Text Block]	December 31, 2017 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 24,200 $ 8,219 $ 34 $ 7 $ — $ — $ 32,460 Unamortized discount (25 ) (3 ) — — — — (28 ) Unamortized premium 1,119 447 — — — — 1,566 Amortized cost 25,294 8,663 34 7 — — 33,998 Gross unrealized gains 98 22 1 — — — 121 Gross unrealized losses (325 ) (141 ) — — — — (466 ) Total available-for-sale securities, at fair value 25,067 8,544 35 7 — — 33,653 Securities remeasured at fair value through earnings: Par value 13,558 7,956 — — 29 801 22,344 Unamortized discount (34 ) — — — (1 ) — (35 ) Unamortized premium 711 415 — — — 33 1,159 Amortized cost 14,235 8,371 — — 28 834 23,468 Gross unrealized gains 26 2 — — 1 42 71 Gross unrealized losses (70 ) (42 ) — — — — (112 ) Total securities remeasured at fair value through earnings 14,191 8,331 — — 29 876 23,427 Total securities, at fair value $ 39,258 $ 16,875 $ 35 $ 7 $ 29 $ 876 $ 57,080 Weighted average coupon as of December 31, 2017 3.67 % 3.73 % 2.84 % 2.50 % 6.55 % 5.26 % 3.71 % Weighted average yield as of December 31, 2017 1 2.84 % 2.87 % 2.02 % 3.08 % 7.30 % 5.19 % 2.89 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 8.4% based on forward rates as of December 31, 2017 . March 31, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 22,893 $ 7,430 $ 32 $ 7 $ — $ — $ 30,362 Unamortized discount (24 ) (3 ) — — — — (27 ) Unamortized premium 1,083 414 — — — — 1,497 Amortized cost 23,952 7,841 32 7 — — 31,832 Gross unrealized gains 13 6 1 — — — 20 Gross unrealized losses (713 ) (273 ) — — — — (986 ) Total available-for-sale securities, at fair value 23,252 7,574 33 7 — — 30,866 Securities remeasured at fair value through earnings: Par value 13,472 9,948 — — 29 814 24,263 Unamortized discount (33 ) (2 ) — — (1 ) (1 ) (37 ) Unamortized premium 672 446 — — — 35 1,153 Amortized cost 14,111 10,392 — — 28 848 25,379 Gross unrealized gains 11 5 — — 1 37 54 Gross unrealized losses (360 ) (256 ) — — — (1 ) (617 ) Total securities remeasured at fair value through earnings 13,762 10,141 — — 29 884 24,816 Total securities, at fair value $ 37,014 $ 17,715 $ 33 $ 7 $ 29 $ 884 $ 55,682 Weighted average coupon as of March 31, 2018 3.66 % 3.69 % 2.87 % 2.50 % 6.55 % 5.50 % 3.70 % Weighted average yield as of March 31, 2018 1 2.88 % 2.93 % 2.02 % 3.03 % 7.36 % 5.51 % 2.93 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 7.6% based on forward rates as of March 31, 2018 .
Components of Investment Securities	The following tables summarize our investment securities as of March 31, 2018 and December 31, 2017 , excluding TBA securities, (dollars in millions). Details of our TBA securities as of each of the respective dates are included in Note 6 . March 31, 2018 December 31, 2017 Investment Securities Amortized Cost Fair Value Amortized Fair Value Agency RMBS: Fixed rate $ 55,266 $ 53,696 $ 55,477 $ 55,026 Adjustable rate 265 268 278 283 CMO 595 590 629 631 Interest-only and principal-only strips 202 208 213 228 Total Agency RMBS 56,328 54,762 56,597 56,168 Non-Agency RMBS 7 7 7 7 CMBS 28 29 28 29 CRT securities 848 884 834 876 Total investment securities $ 57,211 $ 55,682 $ 57,466 $ 57,080 March 31, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 22,893 $ 7,430 $ 32 $ 7 $ — $ — $ 30,362 Unamortized discount (24 ) (3 ) — — — — (27 ) Unamortized premium 1,083 414 — — — — 1,497 Amortized cost 23,952 7,841 32 7 — — 31,832 Gross unrealized gains 13 6 1 — — — 20 Gross unrealized losses (713 ) (273 ) — — — — (986 ) Total available-for-sale securities, at fair value 23,252 7,574 33 7 — — 30,866 Securities remeasured at fair value through earnings: Par value 13,472 9,948 — — 29 814 24,263 Unamortized discount (33 ) (2 ) — — (1 ) (1 ) (37 ) Unamortized premium 672 446 — — — 35 1,153 Amortized cost 14,111 10,392 — — 28 848 25,379 Gross unrealized gains 11 5 — — 1 37 54 Gross unrealized losses (360 ) (256 ) — — — (1 ) (617 ) Total securities remeasured at fair value through earnings 13,762 10,141 — — 29 884 24,816 Total securities, at fair value $ 37,014 $ 17,715 $ 33 $ 7 $ 29 $ 884 $ 55,682 Weighted average coupon as of March 31, 2018 3.66 % 3.69 % 2.87 % 2.50 % 6.55 % 5.50 % 3.70 % Weighted average yield as of March 31, 2018 1 2.88 % 2.93 % 2.02 % 3.03 % 7.36 % 5.51 % 2.93 %
Summary Of Agency Securities Estimated Weighted Average Life Classifications	The following table summarizes our investments as of March 31, 2018 and December 31, 2017 according to their estimated weighted average life classification (dollars in millions): March 31, 2018 December 31, 2017 Estimated Weighted Average Life of Investment Securities Fair Value Amortized Cost Weighted Average Coupon Weighted Average Yield Fair Value Amortized Cost Weighted Average Coupon Weighted Average Yield ≥ 1 year and ≤ 3 years $ 2,671 $ 2,683 3.91% 2.61% $ 2,712 $ 2,693 3.90% 2.67% > 3 years and ≤ 5 years 6,283 6,395 3.23% 2.36% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 42,171 43,513 3.75% 2.98% 45,977 46,398 3.75% 2.95% > 10 years 4,557 4,620 3.79% 3.52% 892 857 4.87% 4.74% Total $ 55,682 $ 57,211 3.70% 2.93% $ 57,080 $ 57,466 3.71% 2.89%
Summary of Continuous Unrealized Loss Position of Available for Sale Securities	The following table presents the gross unrealized loss and fair values of securities classified as available-for-sale by length of time that such securities have been in a continuous unrealized loss position as of March 31, 2018 and December 31, 2017 (in millions): Unrealized Loss Position For Less than 12 Months 12 Months or More Total Securities Classified as Available-for-Sale Fair Value Unrealized Loss Fair Value Unrealized Loss Fair Value Unrealized Loss March 31, 2018 $ 9,782 $ (133 ) $ 18,946 $ (853 ) $ 28,728 $ (986 ) December 31, 2017 $ 3,582 $ (15 ) $ 20,577 $ (451 ) $ 24,159 $ (466 )
Summary of Net Gain from Sale of Agency Securities	The following table is a summary of our net gain (loss) from the sale of investment securities for the three months ended March 31, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended March 31, 2018 2017 Investment Securities Available-for-Sale Securities 2 Fair Value Option Securities Total Available-for-Sale Securities 2 Fair Value Option Securities Total Investment securities sold, at cost $ (387 ) $ (1,003 ) $ (1,390 ) $ (5,149 ) $ (219 ) $ (5,368 ) Proceeds from investment securities sold 1 388 1,000 1,388 5,065 219 5,284 Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) Gross gain on sale of investment securities $ 3 $ 7 $ 10 $ 4 $ — $ 4 Gross loss on sale of investment securities (2 ) (10 ) (12 ) (88 ) — (88 ) Net gain (loss) on sale of investment securities $ 1 $ (3 ) $ (2 ) $ (84 ) $ — $ (84 ) ________________________________ 1. Proceeds include cash received during the period, plus receivable for investment securities sold during the period as of period end. 2. See Note 10 for a summary of changes in accumulated OCI.

Repurchase Agreements and Oth21

Repurchase Agreements and Other Debt (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Repurchase Agreements [Abstract]
Schedule of Borrowings under Repurchase Agreements and Weighted Average Interest Rates	The following table summarizes our borrowings under repurchase agreements by their remaining maturities as of March 31, 2018 and December 31, 2017 (dollars in millions): March 31, 2018 December 31, 2017 Remaining Maturity Repurchase Agreements Weighted Average Interest Rate Weighted Average Days to Maturity Repurchase Agreements Weighted Average Interest Rate Weighted Average Days to Maturity Agency repo: ≤ 1 month $ 24,939 1.79 % 14 $ 19,771 1.59 % 11 > 1 to ≤ 3 months 12,881 1.70 % 57 16,150 1.50 % 50 > 3 to ≤ 6 months 3,381 1.76 % 134 7,287 1.50 % 130 > 6 to ≤ 9 months 485 2.07 % 214 2,361 1.66 % 225 > 9 to ≤ 12 months 3,678 1.96 % 297 202 1.64 % 297 > 12 to ≤ 24 months 2,267 2.29 % 596 1,700 1.84 % 468 > 24 to ≤ 36 months 1,325 2.26 % 937 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 48,956 1.82 % 109 $ 50,296 1.57 % 116

Derivative and Other Hedging 22

Derivative and Other Hedging Instruments (Tables)	3 Months Ended
	Mar. 31, 2018
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/(liabilities) as of March 31, 2018 and December 31, 2017 (in millions): Derivative and Other Hedging Instruments Balance Sheet Location March 31, 2018 December 31, 2017 Interest rate swaps Derivative assets, at fair value $ 174 $ 81 Swaptions Derivative assets, at fair value 153 75 TBA securities Derivative assets, at fair value 83 30 U.S. Treasury futures - short Derivative assets, at fair value — 19 Total derivative assets, at fair value $ 410 $ 205 Interest rate swaps Derivative liabilities, at fair value $ (1 ) $ (1 ) TBA securities Derivative liabilities, at fair value (1 ) (27 ) U.S. Treasury futures - short Derivative liabilities, at fair value (30 ) — Total derivative liabilities, at fair value $ (32 ) $ (28 ) U.S. Treasury securities - long U.S. Treasury securities, at fair value $ 224 $ — U.S. Treasury securities - short Obligation to return securities borrowed under reverse repurchase agreements, at fair value (10,352 ) (10,467 ) Total U.S. Treasury securities, net at fair value $ (10,128 ) $ (10,467 )
Schedule of Interest Rate Swaption Agreements Outstanding	Swaptions Option Underlying Payer Swap Current Option Expiration Date Cost Basis Fair Value Average Months to Current Option Expiration Date 1 Notional Amount Average Fixed Pay Rate Average Receive Rate (LIBOR) Average Term (Years) March 31, 2018 ≤ 1 year $ 110 $ 104 7 $ 5,050 2.74% 3M 8.0 > 1 year ≤ 2 years 24 29 16 1,200 2.83% 3M 8.1 > 2 year ≤ 3 years 18 20 27 500 2.78% 3M 10.0 Total $ 152 $ 153 10 $ 6,750 2.76% 3M 8.2 December 31, 2017 ≤ 1 year $ 118 $ 46 7 $ 5,100 2.71% 3M 8.8 > 1 year ≤ 2 years 23 16 18 1,050 2.71% 3M 8.7 > 2 year ≤ 3 years 18 13 30 500 2.78% 3M 10.0 Total $ 159 $ 75 10 $ 6,650 2.72% 3M 8.9 ________________________________ 1. As of March 31, 2018 and December 31, 2017 , ≤ 1 year notional amount includes $700 million of Bermudan swaptions where the options may be exercised on predetermined dates up to their final exercise date, which is six months prior to the underlying swaps' maturity date. U.S. Treasury Securities March 31, 2018 December 31, 2017 Maturity Face Amount Net Long / (Short) Cost Basis Fair Value Face Amount Net Long / (Short) Cost Basis Fair Value 5 years $ 50 $ 50 $ 54 $ (288 ) $ (286 ) $ (283 ) 7 years (6,451 ) (6,419 ) (6,235 ) (6,131 ) (6,106 ) (6,029 ) 10 years (4,172 ) (4,122 ) (3,947 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities, net $ (10,573 ) $ (10,491 ) $ (10,128 ) $ (10,699 ) $ (10,622 ) $ (10,467 )
US government securities	U.S. Treasury Securities March 31, 2018 December 31, 2017 Maturity Face Amount Net Long / (Short) Cost Basis Fair Value Face Amount Net Long / (Short) Cost Basis Fair Value 5 years $ 50 $ 50 $ 54 $ (288 ) $ (286 ) $ (283 ) 7 years (6,451 ) (6,419 ) (6,235 ) (6,131 ) (6,106 ) (6,029 ) 10 years (4,172 ) (4,122 ) (3,947 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities, net $ (10,573 ) $ (10,491 ) $ (10,128 ) $ (10,699 ) $ (10,622 ) $ (10,467 )
US Government Futures Securities [Table Text Block]	U.S. Treasury Futures March 31, 2018 December 31, 2017 Maturity Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 5 years $ (730 ) $ (831 ) $ (836 ) $ (5 ) $ (730 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,974 ) (1,999 ) (25 ) (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (2,380 ) $ (2,805 ) $ (2,835 ) $ (30 ) $ (2,910 ) $ (3,570 ) $ (3,551 ) $ 19 ________________________________ 1. Net carrying value represents the difference between the fair market value and the cost basis (or the forward price to be paid/(received) for the underlying U.S. Treasury security) of the U.S. Treasury futures contract as of period-end and is reported in derivative assets/(liabilities), at fair value in our consolidated balance sheets.
Summary of Long and Short Position of Derivative Instruments	March 31, 2018 December 31, 2017 TBA Securities by Coupon Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 Notional Amount - Long (Short) Cost Basis Fair Value Net Carrying Value 1 15-Year TBA securities: 2.5% $ 403 $ 390 $ 394 $ 4 $ 1,373 $ 1,372 $ 1,370 $ (2 ) 3.0% 2,774 2,756 2,768 12 3,161 3,225 3,217 (8 ) 3.5% 750 761 764 3 414 428 428 — Total 15-Year TBA securities 3,927 3,907 3,926 19 4,948 5,025 5,015 (10 ) 30-Year TBA securities: 3.0% 3,822 3,690 3,726 36 4,317 4,303 4,312 9 3.5% 3,272 3,259 3,276 17 3,932 4,027 4,034 7 4.0% 2,650 2,709 2,719 10 2,338 2,449 2,446 (3 ) 4.5% (35 ) (36 ) (36 ) — (61 ) (65 ) (65 ) — Total 30-Year TBA securities, net 9,709 9,622 9,685 63 10,526 10,714 10,727 13 Total TBA securities, net $ 13,636 $ 13,529 $ 13,611 $ 82 $ 15,474 $ 15,739 $ 15,742 $ 3 ________________________________ 1. Net carrying value represents the difference between the fair market value and the cost basis (or the forward price to be paid/(received) for the underlying Agency security) 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 following table summarizes 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, 2018 and 2017 (in millions): Derivative and Other Hedging Instruments Beginning Notional Amount Additions Settlement, Termination, Expiration or Exercise Ending Notional Amount Gain/(Loss) on Derivative Instruments and Other Securities, Net 1 Three months ended March 31, 2018: TBA securities, net $ 15,474 43,669 (45,507 ) $ 13,636 $ (292 ) Interest rate swaps $ 43,700 3,150 (1,600 ) $ 45,250 663 Payer swaptions $ 6,650 1,100 (1,000 ) $ 6,750 91 U.S. Treasury securities - short position $ (10,699 ) (662 ) 563 $ (10,798 ) 212 U.S. Treasury securities - long position $ — 959 (734 ) $ 225 — U.S. Treasury futures contracts - short position $ (2,910 ) (2,909 ) 3,439 $ (2,380 ) 62 $ 736 Three months ended March 31, 2017: TBA securities, net $ 10,916 36,096 (32,842 ) $ 14,170 $ 39 Interest rate swaps $ 37,175 1,300 (2,700 ) $ 35,775 22 Payer swaptions $ 1,200 1,000 — $ 2,200 (11 ) U.S. Treasury securities - short position $ (8,061 ) (2,558 ) 1,450 $ (9,169 ) (78 ) U.S. Treasury securities - long position $ 189 303 (492 ) $ — 1 U.S. Treasury futures contracts - short position $ (1,810 ) (1,810 ) 1,810 $ (1,810 ) (12 ) $ (39 ) ________________________________ 1. Amounts above exclude other miscellaneous gains and losses 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 certain characteristics of our derivative and other hedging instruments outstanding as of March 31, 2018 and December 31, 2017 (dollars in millions): March 31, 2018 December 31, 2017 Interest Rate Swaps Notional 1 Average Rate 2 Average Average Notional 1 Average Rate 2 Average Average ≤ 3 years $ 21,075 1.51% 1.90% 1.5 $ 21,025 1.40% 1.46% 1.5 > 3 to ≤ 5 years 8,375 1.84% 1.87% 4.1 6,825 1.82% 1.43% 4.1 > 5 to ≤ 7 years 5,075 2.16% 1.96% 6.0 5,775 2.02% 1.44% 5.9 > 7 to ≤ 10 years 7,550 2.17% 1.88% 8.9 6,650 2.10% 1.42% 9.1 > 10 years 3,175 2.49% 1.91% 12.9 3,425 2.49% 1.45% 12.9 Total $ 45,250 1.82% 1.90% 4.5 $ 43,700 1.74% 1.44% 4.5

Pledged Assets (Tables)

Pledged Assets (Tables)	3 Months Ended
	Mar. 31, 2018
Pledged Assets [Abstract]
Schedule of Securities and Cash Pledged as Collateral from Counterparties [Table Text Block]	As of March 31, 2018 and December 31, 2017 , 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, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements 1 Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 10,712 $ — $ 10,712 $ 10,853 $ — $ 10,853 Cash — 247 247 — 82 82 Total $ 10,712 $ 247 $ 10,959 $ 10,853 $ 82 $ 10,935
Schedule of Financial Instruments Owned and Pledged as Collateral	The following tables summarize our assets pledged as collateral under our funding, derivative and prime broker agreements by type, including securities pledged related to securities sold but not yet settled, as of March 31, 2018 and December 31, 2017 (in millions): March 31, 2018 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 50,996 $ 621 $ 202 $ 410 $ 52,229 U.S. Treasury securities - fair value 3 115 — 49 — 164 Accrued interest on pledged securities 151 2 1 1 155 Restricted cash and cash equivalents 49 — 331 6 386 Total $ 51,311 $ 623 $ 583 $ 417 $ 52,934 December 31, 2017 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 52,497 $ 662 $ 221 $ 519 $ 53,899 U.S. Treasury securities - fair value 3 113 — 72 — 185 Accrued interest on pledged securities 153 2 1 2 158 Restricted cash and cash equivalents 35 — 281 1 317 Total $ 52,798 $ 664 $ 575 $ 522 $ 54,559 ________________________________ 1. Includes $174 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of March 31, 2018 and December 31, 2017 , respectively. 2. Includes margin for TBAs cleared through prime brokers and other clearing deposits. 3. Includes repledged securities received as collateral from counterparties.
Schedules Of Securities Pledged As Collateral Under Repurchase Agreement	The following table summarizes our securities pledged as collateral under our repurchase agreements by the remaining maturity of our borrowings, including securities pledged related to sold but not yet settled securities, as of March 31, 2018 and December 31, 2017 (in millions). For the corresponding borrowings associated with the following amounts and the interest rates thereon, refer to Note 5 . March 31, 2018 December 31, 2017 Securities Pledged by Remaining Maturity of Repurchase Agreements Fair Value of Pledged Securities Amortized Cost of Pledged Securities Accrued Interest on Pledged Securities Fair Value of Pledged Securities Amortized Cost of Pledged Securities Accrued Interest on Pledged Securities RMBS: 1,2 ≤ 30 days $ 25,229 $ 25,939 $ 75 $ 20,162 $ 20,313 $ 59 > 30 and ≤ 60 days 8,001 8,249 24 12,950 13,061 38 > 60 and ≤ 90 days 5,561 5,724 17 4,000 4,013 11 > 90 days 12,205 12,570 36 15,385 15,512 45 Total RMBS $ 50,996 $ 52,482 $ 152 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $174 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of March 31, 2018 and December 31, 2017 , respectively. 2. March 31, 2018 amounts exclude $115 million
Offsetting Assets and Liabilities	The following tables present information about our assets and liabilities that are subject to master netting arrangements and can potentially be offset on our consolidated balance sheets as of March 31, 2018 and December 31, 2017 (in millions): Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Received 2 March 31, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 327 $ — $ 327 $ (1 ) $ (243 ) $ 83 TBA securities, at fair value 83 — 83 (1 ) — 82 Receivable under reverse repurchase agreements 10,770 — 10,770 (7,606 ) (3,164 ) — Total $ 11,180 $ — $ 11,180 $ (7,608 ) $ (3,407 ) $ 165 December 31, 2017 Interest rate swap and swaption agreements, at fair value 1 $ 156 $ — $ 156 $ (1 ) $ (82 ) $ 73 TBA securities, at fair value 30 — 30 (22 ) — 8 Receivable under reverse repurchase agreements 10,961 — 10,961 (9,682 ) (1,279 ) — Total $ 11,147 $ — $ 11,147 $ (9,705 ) $ (1,361 ) $ 81
Offsetting Liabilities	Offsetting of Financial 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 in the Consolidated Balance Sheets Net Amount Financial Instruments Collateral Pledged 2 March 31, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 1 — 1 (1 ) — — Repurchase agreements 48,956 — 48,956 (7,606 ) (41,350 ) — Total $ 48,958 $ — $ 48,958 $ (7,608 ) $ (41,350 ) $ — December 31, 2017 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 27 — 27 (22 ) (5 ) — Repurchase agreements and FHLB advances 50,296 — 50,296 (9,682 ) (40,614 ) — Total $ 50,324 $ — $ 50,324 $ (9,705 ) $ (40,619 ) $ — ________________________________ 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 pledged / received 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, 2018
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, 2018 and December 31, 2017 based on their categorization within the valuation hierarchy (in millions). There were no transfers between valuation hierarchy levels during the periods presented. March 31, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Agency securities $ — $ 54,141 $ — $ — $ 55,506 $ — Agency securities transferred to consolidated VIEs — 621 — — 662 — Credit risk transfer securities — 884 — — 876 — Non-Agency securities — 36 — — 36 — U.S. Treasury securities 224 — — — — — REIT equity securities 42 — — 29 — — Interest rate swaps — 174 — — 81 — Swaptions — 153 — — 75 — TBA securities — 83 — — 30 — U.S. Treasury futures — — — 19 — — Total $ 266 $ 56,092 $ — $ 48 $ 57,266 $ — Liabilities: Debt of consolidated VIEs $ — $ 336 $ — $ — $ 357 $ — Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements 10,352 — — 10,467 — — Interest rate swaps — 1 — — 1 — TBA securities — 1 — — 27 — U.S. Treasury futures 30 — — — — — Total $ 10,352 $ 338 $ — $ 10,467 $ 385 $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes changes to accumulated OCI for the three months ended March 31, 2018 and 2017 (in millions): Three Months Ended March 31, Accumulated Other Comprehensive Income (Loss) 2018 2017 Beginning Balance $ (345 ) $ (397 ) OCI before reclassifications (620 ) (38 ) (Gain) loss amounts for available-for-sale securities reclassified from accumulated OCI to realized gain (loss) on sale of investment securities (1 ) 84 Ending Balance $ (966 ) $ (351 )

Organization (Details)

Organization (Details)	3 Months Ended
	Mar. 31, 2018
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 Accoun27

Summary of Significant Accounting Policies (Details)	3 Months Ended
	Mar. 31, 2018
Derivative [Line Items]
Document Period End Date	Mar. 31, 2018
Required Annual Distribution of Taxable Net Income	90.00%

Investment Securities (Narrativ

Investment Securities (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Document Period End Date	Mar. 31, 2018
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	$ 55,682	$ 57,080
Weighted average expected constant prepayment rate	8.00%	8.00%
Agency securities, total fair value	$ 600
Variable Interest Entity, Consolidated, Carrying Amount, Assets	(621)	$ (662)
Debt, at fair value	(336)	(357)
Fair value of CMO securities and interest-only and principal-only strips	800	900
Securitized CMO Securities	1,100	1,200
CMO and Interest Only, Principal Only Securities, Maximum Loss Exposure	91	124
Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Unamortized premium balance	2,600	2,700
TBA securities Fifteen Year and Thirty Year Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Net long TBA position, at fair value	13,600	15,700
TBA, net carrying value	$ 82	$ 3
Credit Risk Transfer Securities [Member] | Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted Average Coupon Rate	3.70%	3.90%
Underlying Collateral Coupon	3.60%	3.60%
Credit Risk Transfer Securities [Member] | Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Weighted Average Coupon Rate	8.80%	8.50%
Underlying Collateral Coupon	4.40%	4.40%

Investment Securities (Summary

Investment Securities (Summary of Investment in Agency Security) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Document Period End Date	Mar. 31, 2018
Amortized cost	$ 57,211	$ 57,466
Mortgage Backed Securities Amortized Cost	57,211	57,466
Fair value	55,682	57,080
Total agency MBS, amortized cost	56,328	56,597
Total agency MBS, at fair value	54,762	56,168
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	55,682	57,080
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Amortized cost	7	7
Fair value	7	7
Commercial Mortgage Backed Securities [Member]
Amortized cost	28	28
Fair value	29	29
Credit Risk Transfer Securities [Member]
Interest-only and principal-only strips, amortized cost	848	834
Interest-only and principal-only strips, fair value	884	876
Fixed Income Securities [Member] | Agency Securities [Member]
Amortized cost	55,266	55,477
Fair value	53,696	55,026
Adjustable-Rate [Member] | Agency Securities [Member]
Amortized cost	265	278
Fair value	268	283
Collateralized Mortgage Obligations [Member] | Agency Securities [Member]
Amortized cost	595	629
Fair value	590	631
Interest Only And Principal Only Strip [Member] | Agency Securities [Member]
Interest-only and principal-only strips, amortized cost	202	213
Interest-only and principal-only strips, fair value	$ 208	$ 228

Investment Securities (Componen

Investment Securities (Components Of Investment Securities) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Document Period End Date	Mar. 31, 2018
Agency securities transferred to consolidated VIEs	$ 621	$ 662
Amortized cost	57,211	57,466
Total agency MBS, at fair value	54,762	56,168
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	$ 55,682	$ 57,080
Weighted average coupon	3.70%	3.71%
Weighted average yield	2.93%	2.89%
Future Prepayment Rate Assumption Of Investment Portfolio	8.00%	8.00%
Mortgage Backed Securities Amortized Cost	$ 57,211	$ 57,466
Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	30,362	32,460
Unamortized discount	(27)	(28)
Unamortized premium	1,497	1,566
Amortized cost	31,832	33,998
Gross unrealized gains	20	121
Gross unrealized losses	(986)	(466)
Total available-for-sale securities, at fair value	30,866	33,653
Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	25,379	23,468
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	54	71
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	(617)	(112)
Securities Remeasured at Fair Value Through Earnings, Debt Securities	24,816	23,427
Securities remeasured at fair value through earnings, Par Value	24,263	22,344
Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	(37)	(35)
Unamortized premium	1,153	1,159
Fannie Mae [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	$ 37,014	$ 39,258
Weighted average coupon	3.66%	3.67%
Weighted average yield	2.88%	2.84%
Fannie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 22,893	$ 24,200
Unamortized discount	(24)	(25)
Unamortized premium	1,083	1,119
Amortized cost	23,952	25,294
Gross unrealized gains	13	98
Gross unrealized losses	(713)	(325)
Total available-for-sale securities, at fair value	23,252	25,067
Fannie Mae [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	14,111	14,235
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	11	26
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	(360)	(70)
Securities Remeasured at Fair Value Through Earnings, Debt Securities	13,762	14,191
Securities remeasured at fair value through earnings, Par Value	13,472	13,558
Fannie Mae [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	(33)	(34)
Unamortized premium	672	711
Freddie Mac [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	$ 17,715	$ 16,875
Weighted average coupon	3.69%	3.73%
Weighted average yield	2.93%	2.87%
Freddie Mac [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 7,430	$ 8,219
Unamortized discount	(3)	(3)
Unamortized premium	414	447
Amortized cost	7,841	8,663
Gross unrealized gains	6	22
Gross unrealized losses	(273)	(141)
Total available-for-sale securities, at fair value	7,574	8,544
Freddie Mac [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	10,392	8,371
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	5	2
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	(256)	(42)
Securities Remeasured at Fair Value Through Earnings, Debt Securities	10,141	8,331
Securities remeasured at fair value through earnings, Par Value	9,948	7,956
Freddie Mac [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	(2)	0
Unamortized premium	446	415
Ginnie Mae [Member]
Schedule of Investments [Line Items]
Total agency MBS, at fair value	$ 33	$ 35
Weighted average coupon	2.87%	2.84%
Weighted average yield	2.02%	2.02%
Ginnie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 32	$ 34
Unamortized discount	0	0
Unamortized premium	0	0
Amortized cost	32	34
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Total available-for-sale securities, at fair value	33	35
Ginnie Mae [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	0	0
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	0	0
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	0	0
Securities Remeasured at Fair Value Through Earnings, Debt Securities	0	0
Securities remeasured at fair value through earnings, Par Value	0	0
Ginnie Mae [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	0	0
Unamortized premium	0	0
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Investments [Line Items]
Amortized cost	7	7
Total Securities	$ 7	$ 7
Weighted average coupon	2.50%	2.50%
Weighted average yield	3.03%	3.08%
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 7	$ 7
Unamortized discount	0	0
Unamortized premium	0	0
Amortized cost	7	7
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Total available-for-sale securities, at fair value	7	7
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	0	0
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	0	0
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	0	0
Securities Remeasured at Fair Value Through Earnings, Debt Securities	0	0
Securities remeasured at fair value through earnings, Par Value	0	0
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	0	0
Unamortized premium	0	0
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Amortized cost	28	28
Total Securities	$ 29	$ 29
Weighted average coupon	6.55%	6.55%
Weighted average yield	7.36%	7.30%
Commercial Mortgage Backed Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 0	$ 0
Unamortized discount	0	0
Unamortized premium	0	0
Amortized cost	0	0
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Total available-for-sale securities, at fair value	0	0
Commercial Mortgage Backed Securities [Member] | Agency securities remeasured at fair value through earnings [Member]
Schedule of Investments [Line Items]
Securities Remeasured at Fair Value through earnings, Amortized Cost	28	28
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	1	1
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	0	0
Securities Remeasured at Fair Value Through Earnings, Debt Securities	29	29
Securities remeasured at fair value through earnings, Par Value	29	29
Commercial Mortgage Backed Securities [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	(1)	(1)
Unamortized premium	0	0
Credit Risk Transfer Securities [Member]
Schedule of Investments [Line Items]
Trading Securities, Cost	$ 848	$ 834
Weighted average coupon	5.50%	5.26%
Weighted average yield	5.51%	5.19%
Trading Securities, Other	$ 884	$ 876
Credit Risk Transfer Securities [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	0	0
Unamortized discount	0	0
Unamortized premium	0	0
Amortized cost	0	0
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Total available-for-sale securities, at fair value	0	0
Credit Risk Transfer Securities [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Unamortized discount	(1)	0
Unamortized premium	35	33
Securities Remeasured at Fair Value through earnings, Amortized Cost	848	834
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Gain	37	42
Securities Remeasured at Fair Value Through Earnings, Gross Unrealized Loss	(1)	0
Securities Remeasured at Fair Value Through Earnings, Debt Securities	884	876
Securities remeasured at fair value through earnings, Par Value	814	801
Total Securities	$ 884	$ 876

Investment Securities (Summar31

Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Document Period End Date	Mar. 31, 2018
Agency securities classified as available for sale, Fair value	$ 55,682	$ 57,080
Agency securities classified as available for sale, Amortized cost	$ 57,211	$ 57,466
Weighted Average Coupon	3.70%	3.71%
Weighted Average Yield	2.93%	2.89%
Greater Than One Year and Less Than or Equal to Three Years [Member]
Fair Value	$ 2,671	$ 2,712
Amortized Cost	$ 2,683	$ 2,693
Weighted Average Coupon	3.91%	3.90%
Weighted Average Yield	2.61%	2.67%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Fair Value	$ 6,283	$ 7,499
Amortized Cost	$ 6,395	$ 7,518
Weighted Average Coupon	3.23%	3.31%
Weighted Average Yield	2.36%	2.39%
Greater Than Five Years [Member]
Fair Value	$ 42,171	$ 45,977
Amortized Cost	$ 43,513	$ 46,398
Weighted Average Coupon	3.75%	3.75%
Weighted Average Yield	2.98%	2.95%
Greater Than Ten Years [Member]
Fair Value	$ 4,557	$ 892
Amortized Cost	$ 4,620	$ 857
Weighted Average Coupon	3.79%	4.87%
Weighted Average Yield	3.52%	4.74%

Investment Securities (Summar32

Investment Securities (Summary Of Changes In Accumulated OCI For Available-For-Sale Security) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized Gains and (Losses), Net	$ (621)	$ 46
Agency Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning OCI Balance	(345)	(397)
Unrealized Gains and (Losses), Net	(620)	(38)
Reversal of Unrealized (Gains) and Losses, Net on Realization	(1)	84
Ending OCI Balance	$ (966)	$ (351)

Investment Securities (Summar33

Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Document Period End Date	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Member]
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$ 9,782	$ 3,582
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	(133)	(15)
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	18,946	20,577
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	(853)	(451)
Unrealized Loss Position For - Estimated Fair Value - Total	28,728	24,159
Unrealized Loss Position For - Unrealized Loss - Total	$ (986)	$ (466)

Investment Securities (Summar34

Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cost of Sale of Fair Value Option Securities	$ (1,003)	$ (219)
Cost of Sale of Investment Securities	(1,390)	(5,368)
Proceeds from agency MBS sold	1,403	2,999
Net gain (loss) on sale of investment securities	(2)	(84)
Available-for-sale Securities [Member]
Agency MBS sold, at cost	(387)	(5,149)
Proceeds from agency MBS sold	388	5,065
Net gain (loss) on sale of investment securities		(84)
Gross gain on sale of investment securities	3	4
Gross loss on sale of investment securities	(2)	(88)
Securities Remeasured at Fair Value [Member]
Proceeds from agency MBS sold	1,000	219
Net gain (loss) on sale of investment securities		0
Gross gain on sale of investment securities	7	0
Gross loss on sale of investment securities	(10)	0
Securities (Assets) [Member]
Proceeds from agency MBS sold	1,388	5,284
Net gain (loss) on sale of investment securities	(2)	(84)
Gross gain on sale of investment securities	10	4
Gross loss on sale of investment securities	(12)	$ (88)
Cost and Proceeds of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	1
Cost and Proceeds of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	(3)
Gross Gain & Loss of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	1
Gross Gain & Loss of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	$ (3)

Investment Securities Securitie

Investment Securities Securities by Credit Rating (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Document Period End Date	Mar. 31, 2018
Securities Remeasured at Fair Value [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	$ 884	$ 876
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	30,866	33,653
Available-for-sale Securities [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	7	7
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Available-for-sale Securities [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Debt Securities	0	0
Agency securities remeasured at fair value through earnings [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	24,816	23,427
Agency securities remeasured at fair value through earnings [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	0	0
Agency securities remeasured at fair value through earnings [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	29	29
BBB Rating [Member] | Commercial Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	29	29
BBB Rating [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	26	20
BB Rating [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	139	136
AAA Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	7	7
B Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	0	0
B Rating [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	698	691
Not Rated [Member] | Credit Risk Transfer Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities Remeasured at Fair Value Through Earnings, Debt Securities	$ 21	$ 29

Repurchase Agreements And Oth36

Repurchase Agreements And Other Debt (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Document Period End Date	Mar. 31, 2018
Securities Sold under Agreements to Repurchase	$ 48,956	$ 50,296
Debt of consolidated variable interest entities, at fair value	(336)	(357)
TBA securities Fifteen Year and Thirty Year Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Fair Value, Net	82	3
TBA and Forward Settling Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Forward Settlement Value	13,529	15,739
Derivative, Fair Value, Net	82	$ 3
Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 48,956

Repurchase Agreements And Oth37

Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2018USD ($)days	Dec. 31, 2017USD ($)days
Document Period End Date	Mar. 31, 2018
Repurchase Agreements	$ 48,956	$ 50,296
Maturity Overnight [Member]
Repurchase Agreements	3,650	5,250
30 Days or Less [Member]
Repurchase Agreements	$ 24,939	$ 19,771
Weighted Average Interest Rate	1.79%	1.59%
Weighted Average Days to Maturity | days	14	11
1 to 3 Months
Repurchase Agreements	$ 12,881	$ 16,150
Weighted Average Interest Rate	1.70%	1.50%
Weighted Average Days to Maturity | days	57	50
3 to 6 Months
Repurchase Agreements	$ 3,381	$ 7,287
Weighted Average Interest Rate	1.76%	1.50%
Weighted Average Days to Maturity | days	134	130
6 to 9 Months
Repurchase Agreements	$ 485	$ 2,361
Weighted Average Interest Rate	2.07%	1.66%
Weighted Average Days to Maturity | days	214	225
9 to 12 Months
Repurchase Agreements	$ 3,678	$ 202
Weighted Average Interest Rate	1.96%	1.64%
Weighted Average Days to Maturity | days	297	297
12 to 24 Months
Repurchase Agreements	$ 2,267	$ 1,700
Weighted Average Interest Rate	2.29%	1.84%
Weighted Average Days to Maturity | days	596	468
24 to 36 Months
Repurchase Agreements	$ 1,325	$ 2,200
Weighted Average Interest Rate	2.26%	1.80%
Weighted Average Days to Maturity | days	937	803
36 to 48 months
Repurchase Agreements	$ 0	$ 625
Weighted Average Interest Rate	0.00%	1.90%
Weighted Average Days to Maturity | days	0	1,141
Agency Securities [Member]
Repurchase Agreements	$ 48,956
Weighted Average Days to Maturity | days	109	116
Agency Securities [Member] | Repurchase Agreements [Member]
Weighted Average Interest Rate	1.82%	1.57%

Derivative and Other Hedging 38

Derivative and Other Hedging Instruments (Narrative) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)month	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)month	Dec. 31, 2016USD ($)
Interest Rate Swaption [Member]
Average Maturity (Years)	8 years 2 months 12 days		8 years 10 months 24 days
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	10		10
Notional Amount	$ 6,750		$ 6,650
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	91	$ (11)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	1,100	1,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	$ (1,000)	0
Derivative, Average Fixed Interest Rate	2.76%		2.72%
Interest Rate Derivatives, at Fair Value, Net	$ 153		$ 75
Options At Cost	152		159
TBA and Forward Settling Agency Securities [Member]
Notional Amount	13,636	14,170	15,474	$ 10,916
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(292)	39
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	43,669	36,096
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(32,842)
US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	62	(12)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	736	(39)
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Notional Amount	6,750
Short [Member] | US Treasury Securities [Member]
Notional Amount	10,798	9,169	10,699	8,061
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	212	(78)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	(662)	2,558
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	563	(1,450)
Long [Member] | US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	1
Trading Securities Added During the Period	959	303
Notional Amount Of Trading Securities Settlement Expiration During The Period	(734)	(492)
Trading Securities		$ 0	$ 0	$ 189
Long [Member]
Trading Securities	$ 225

Derivative and Other Hedging 39

Derivative and Other Hedging Instruments (Fair Value Information) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative asset, fair value	$ 410		$ 205
Derivative liability, fair value	(32)		(28)
Derivative assets, at fair value	410		205
Derivative Liability	(32)		(28)
U.S. Treasury securities	224		0
U.S. Treasury Securities - short	(10,352)		(10,467)
Total - (short)/long, net	(10,128)		(10,467)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	736	$ (39)
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	13,636	14,170	15,474	$ 10,916
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	43,669	36,096
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(32,842)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(292)	39
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	45,250		43,700
Derivative liability, fair value	(1)		(1)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	3,150	1,300
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(1,600)	(2,700)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	663	22
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	174		81
Interest Rate Swaption [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	6,750		6,650
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	1,100	1,000
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(1,000)	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	91	(11)
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	153		75
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative liability, fair value	(1)		(27)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(45,507)
US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	62	(12)
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Future [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative [Line Items]
Derivative liability, fair value	(30)		0
Derivative assets, at fair value	0		19
Derivative Liability	(30)
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	83		30
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	45,250
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	6,750
Short [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	10,798	9,169	10,699	8,061
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	(662)	2,558
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	563	(1,450)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	212	(78)
Long [Member]
Derivative [Line Items]
Trading Securities	225
Long [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	1
Trading Securities		0	$ 0	$ 189
Trading Securities Added During the Period	959	303
Notional Amount Of Trading Securities Settlement Expiration During The Period	$ (734)	$ (492)

Derivative and Other Hedging 40

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)month	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)month
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 736	$ (39)
Payer Swaption [Member]
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M		3M
Interest Rate Swaption [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 91	(11)
Notional Amount	$ 6,750		$ 6,650
Average Fixed Pay Rate	2.76%		2.72%
Options At Cost	$ 152		$ 159
Interest Rate Derivatives, at Fair Value, Net	$ 153		$ 75
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	10		10
Average Maturity (Years)	8 years 2 months 12 days		8 years 10 months 24 days
Forward Contracts [Member] | Interest Rate Swap [Member]
Derivative, Notional Amount	$ 2,500		$ 4,600
Weighted Average Forward Start Date	4 months 24 days		3 months 18 days
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 663	$ 22
Notional Amount	$ 45,250		$ 43,700
Average Fixed Pay Rate	1.82%		1.74%
Average Receive Rate	1.90%		1.44%
Average Maturity (Years)	4 years 6 months		4 years 6 months
Less Than or Equal to One Year [Member] | Payer Swaption [Member]
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M		3M
Less Than or Equal to One Year [Member] | Interest Rate Swaption [Member]
Notional Amount	$ 5,050		$ 5,100
Average Fixed Pay Rate	2.74%		2.71%
Options At Cost	$ 110		$ 118
Interest Rate Derivatives, at Fair Value, Net	$ 104		$ 46
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	7		7
Average Maturity (Years)	8 years		8 years 9 months 18 days
Greater Than One Year and Less Than or Equal to Two Years [Member] | Payer Swaption [Member]
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M		3M
Greater Than One Year and Less Than or Equal to Two Years [Member] | Interest Rate Swaption [Member]
Notional Amount	$ 1,200		$ 1,050
Average Fixed Pay Rate	2.83%		2.71%
Options At Cost	$ 24		$ 23
Interest Rate Derivatives, at Fair Value, Net	$ 29		$ 16
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	16		18
Average Maturity (Years)	8 years 1 month 6 days		8 years 8 months 12 days
Greater Than Two Years and Less Than or Equal to Three Years [Member] | Payer Swaption [Member]
Interest Rate Derivative Not Designated As Hedging Instruments Receive Rate	3M		3M
Greater Than Two Years and Less Than or Equal to Three Years [Member] | Interest Rate Swaption [Member]
Notional Amount	$ 500		$ 500
Average Fixed Pay Rate	2.78%		2.78%
Options At Cost	$ 18		$ 18
Interest Rate Derivatives, at Fair Value, Net	$ 20		$ 13
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month	27		30
Average Maturity (Years)	10 years		10 years
Greater Than One Year and Less Than or Equal to Three Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 21,075		$ 21,025
Average Fixed Pay Rate	1.51%		1.40%
Average Receive Rate	1.90%		1.46%
Average Maturity (Years)	1 year 6 months		1 year 6 months
Greater Than Three Years and Less Than or Equal to Five Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 8,375		$ 6,825
Average Fixed Pay Rate	1.84%		1.82%
Average Receive Rate	1.87%		1.43%
Average Maturity (Years)	4 years 1 month 6 days		4 years 1 month 6 days
Greater Than Five Years and Less than or Equal to Seven Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 5,075		$ 5,775
Average Fixed Pay Rate	2.16%		2.02%
Average Receive Rate	1.96%		1.44%
Average Maturity (Years)	6 years		5 years 10 months 24 days
Greater Than Seven Years and Less than or Equal to Ten Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 7,550		$ 6,650
Average Fixed Pay Rate	2.17%		2.10%
Average Receive Rate	1.88%		1.42%
Average Maturity (Years)	8 years 10 months 24 days		9 years 1 month 6 days
Greater Than Ten Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 3,175		$ 3,425
Average Fixed Pay Rate	2.49%		2.49%
Average Receive Rate	1.91%		1.45%
Average Maturity (Years)	12 years 10 months 24 days		12 years 10 months 24 days

Derivative and Other Hedging 41

Derivative and Other Hedging Instruments (Remaining Interest Rate Swap Term) (Details) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018USD ($)month	Mar. 31, 2017USD ($)	Dec. 31, 2017USD ($)month
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 736	$ (39)
Interest Rate Swaption [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	91	(11)
Cost	152		$ 159
Fair Value	$ 153		$ 75
Average Months to Expiration | month	10		10
Derivative Liability, Notional Amount	$ 6,750		$ 6,650
Average Fixed Pay Rate	2.76%		2.72%
Average Maturity (Years)	8 years 2 months 12 days		8 years 10 months 24 days
Payer Swaption [Member]
Average Receive Rate (LIBOR)	3M		3M
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 663	$ 22
Derivative Liability, Notional Amount	$ 45,250		$ 43,700
Average Fixed Pay Rate	1.82%		1.74%
Average Maturity (Years)	4 years 6 months		4 years 6 months
Less Than or Equal to One Year [Member] | Interest Rate Swaption [Member]
Cost	$ 110		$ 118
Fair Value	$ 104		$ 46
Average Months to Expiration | month	7		7
Derivative Liability, Notional Amount	$ 5,050		$ 5,100
Average Fixed Pay Rate	2.74%		2.71%
Average Maturity (Years)	8 years		8 years 9 months 18 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 Swap [Member]
Derivative Liability, Notional Amount	$ 21,075		$ 21,025
Average Fixed Pay Rate	1.51%		1.40%
Average Maturity (Years)	1 year 6 months		1 year 6 months
Interest Rate Swaps Excluding Forward Starting [Member] | Interest Rate Swap [Member]
Average Fixed Pay Rate	1.77%		1.68%

Derivative and Other Hedging 42

Derivative and Other Hedging Instruments (US Treasury Securities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
U.S. Treasury securities, net	$ (10,128)	$ (10,467)
7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(6,451)	(6,131)
At Par Value [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(10,573)	(10,699)
US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	(30)	19
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(13,636)	(15,474)
Derivative, Forward Settlement Value	(13,529)	(15,739)
Derivative Asset, Fair Value, Gross Asset	(13,611)	(15,742)
Derivative, Fair Value, Net	82	3
5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	50	(288)
10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(4,172)	(4,280)
10 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	(25)	15
5 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	(5)	4
Short [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(2,380)	(2,910)
Derivative, Forward Settlement Value	(2,805)	(3,570)
Derivative Asset, Fair Value, Gross Asset	(2,835)	(3,551)
Short [Member] | 10 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(1,650)	(2,180)
Derivative, Forward Settlement Value	(1,974)	(2,718)
Derivative Asset, Fair Value, Gross Asset	(1,999)	(2,703)
Short [Member] | 5 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(730)	(730)
Derivative, Forward Settlement Value	(831)	(852)
Derivative Asset, Fair Value, Gross Asset	(836)	(848)
Fair Value Hedging [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(10,128)	(10,467)
Fair Value Hedging [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(6,235)	(6,029)
Fair Value Hedging [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	54	(283)
Fair Value Hedging [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(3,947)	(4,155)
At Cost Basis [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(10,491)	(10,622)
At Cost Basis [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(6,419)	(6,106)
At Cost Basis [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	50	(286)
At Cost Basis [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	$ (4,122)	$ (4,230)

Derivative and Other Hedging 43

Derivative and Other Hedging Instruments (TBA Securities by Coupon and Issuer) (Details) - TBA and Forward Settling Agency Securities [Member] - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative, Notional Amount	$ (13,636)	$ (15,474)
Cost Basis	(13,529)	(15,739)
Net long TBA position, at fair value	(13,611)	(15,742)
TBA, net carrying value	82	3
30 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	(9,709)	(10,526)
Cost Basis	(9,622)	(10,714)
Net long TBA position, at fair value	(9,685)	(10,727)
TBA, net carrying value	63	13
30 Year Maturity [Member] | 3.0% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(3,822)	(4,317)
Cost Basis	(3,690)	(4,303)
Net long TBA position, at fair value	(3,726)	(4,312)
TBA, net carrying value	36	9
30 Year Maturity [Member] | 3.5% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(3,272)	(3,932)
Cost Basis	(3,259)	(4,027)
Net long TBA position, at fair value	(3,276)	(4,034)
TBA, net carrying value	17	7
30 Year Maturity [Member] | 4.0% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(2,650)	(2,338)
Cost Basis	(2,709)	(2,449)
Net long TBA position, at fair value	(2,719)	(2,446)
TBA, net carrying value	10	(3)
30 Year Maturity [Member] | 4.5% Coupon [Member]
Derivative [Line Items]
TBA, net carrying value	0	0
30 Year Maturity [Member] | Short [Member] | 4.5% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(35)	(61)
Cost Basis	(36)	(65)
Net long TBA position, at fair value	(36)	(65)
15 Year Maturity [Member]
Derivative [Line Items]
Derivative, Notional Amount	(3,927)	(4,948)
Cost Basis	(3,907)	(5,025)
Net long TBA position, at fair value	(3,926)	(5,015)
TBA, net carrying value	19	(10)
15 Year Maturity [Member] | 2.5% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(403)	(1,373)
Cost Basis	(390)	(1,372)
Net long TBA position, at fair value	(394)	(1,370)
TBA, net carrying value	4	(2)
15 Year Maturity [Member] | 3.0% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(2,774)	(3,161)
Cost Basis	(2,756)	(3,225)
Net long TBA position, at fair value	(2,768)	(3,217)
TBA, net carrying value	12	(8)
15 Year Maturity [Member] | 3.5% Coupon [Member]
Derivative [Line Items]
Derivative, Notional Amount	(750)	(414)
Cost Basis	(761)	(428)
Net long TBA position, at fair value	(764)	(428)
TBA, net carrying value	$ 3	$ 0

Derivative and Other Hedging 44

Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Comprehensive Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	$ 736	$ (39)
Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(6,650)
Additions	(1,100)	(1,000)
Settlement, Expirations or Exercise	1,000	0
Notional Amount	(6,750)
Amount Gain/(Loss) Recognized in Income on Derivatives	91	(11)
TBA and Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(15,474)	(10,916)
Additions	(43,669)	(36,096)
Settlement, Expirations or Exercise		32,842
Notional Amount	(13,636)	(14,170)
Amount Gain/(Loss) Recognized in Income on Derivatives	(292)	39
Derivative, Notional Amount	(13,636)		$ (15,474)
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Settlement, Expirations or Exercise	45,507
Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(43,700)
Additions	(3,150)	(1,300)
Settlement, Expirations or Exercise	1,600	2,700
Notional Amount	(45,250)
Amount Gain/(Loss) Recognized in Income on Derivatives	663	22
US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	62	(12)
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(6,750)
Derivative, Notional Amount		(2,200)	(6,650)	$ (1,200)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(45,250)
Derivative, Notional Amount		(35,775)	(43,700)	(37,175)
Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(10,699)	(8,061)
Additions	662	(2,558)
Settlement, Expirations or Exercise	(563)	1,450
Notional Amount	(10,798)	(9,169)
Amount Gain/(Loss) Recognized in Income on Derivatives	212	(78)
Derivative, Notional Amount	(2,380)		(2,910)
Long [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Trading Securities	225
Long [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	0	1
Trading Securities		0	$ 0	$ 189
Trading Securities Added During the Period	959	303
Notional Amount Of Trading Securities Settlement Expiration During The Period	(734)	(492)
Future [Member] | Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(2,910)	(1,810)
Additions	2,909	(1,810)
Settlement, Expirations or Exercise	(3,439)	1,810
Notional Amount	$ (2,380)	$ (1,810)

Pledged Assets (Narrative) (Det

Pledged Assets (Narrative) (Details)	Mar. 31, 2018USD ($)
Pledged Assets [Abstract]
Risk Of Repurchase Agreement To Stockholders Equity	5.00%
Risk of interest swap and swaption agreements to stockholders' equity	$ 0.01

Pledged Assets Repurchase Agree

Pledged Assets Repurchase Agreements with Counterparties Greater than or Equal to 5% of Equity at Risk (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Repurchase Agreements with Counterparties Greater than or equal to 5% of Equity at Risk [Line Items]
Securities Sold under Agreements to Repurchase	$ 48,956	$ 50,296
Risk Of Repurchase Agreement To Stockholders Equity	5.00%

Pledged Assets (Assets Pledged

Pledged Assets (Assets Pledged as Collateral) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Retained Interests in Consolidated VIE's Pledged as Collateral Under Repurchase Agreements	$ 174	$ 182
Available-for-sale Securities Pledged as Collateral	51,434	53,055
Accrued interest on pledged securities	155	158
Restricted cash and cash equivalents	386	317
Total Fair Value of Securities Pledged and Accrued Interest	52,934
Total Fair Value Of Agency Securities Pledged And Accrued Interest		54,559
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	50,996	52,497
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	202	221
Accrued interest on pledged securities		1
Restricted cash and cash equivalents	331	281
Total Fair Value of Securities Pledged and Accrued Interest	583
Total Fair Value Of Agency Securities Pledged And Accrued Interest		575
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Accrued interest on pledged securities	151	153
Total Fair Value of Securities Pledged and Accrued Interest	51,311
Total Fair Value Of Agency Securities Pledged And Accrued Interest		52,798
Variable Interest Entity, Primary Beneficiary [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	621	662
Accrued interest on pledged securities	2	2
Total Fair Value of Securities Pledged and Accrued Interest	623
Total Fair Value Of Agency Securities Pledged And Accrued Interest		664
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	410	519
Accrued interest on pledged securities	1	2
Total Fair Value of Securities Pledged and Accrued Interest	417
Total Fair Value Of Agency Securities Pledged And Accrued Interest		522
Includes Sold But Not Yet Settled Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	52,229	53,899
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	164	185
US Treasury Securities [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	115	113
US Treasury Securities [Member] | Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	49	72
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Accrued interest on pledged securities	1
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash and cash equivalents	49	35
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash and cash equivalents	6	1
Excluding Cash Received [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash and cash equivalents	$ 386	$ 317

Pledged Assets (Securities Pled

Pledged Assets (Securities Pledged as Collateral) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Retained Interests in Consolidated VIE's Pledged as Collateral Under Repo	$ 174	$ 182
Maturity Less than 30 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	25,229	20,162
Agency Securities Pledged As Collateral Amortized Cost	25,939	20,313
Agency Securities Pledged As Collateral Accrued Interest	75	59
Maturity 31 To 59 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	8,001	12,950
Agency Securities Pledged As Collateral Amortized Cost	8,249	13,061
Agency Securities Pledged As Collateral Accrued Interest	24	38
Maturity 60 To 90 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	5,561	4,000
Agency Securities Pledged As Collateral Amortized Cost	5,724	4,013
Agency Securities Pledged As Collateral Accrued Interest	17	11
Maturity over 90 days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	12,205	15,385
Agency Securities Pledged As Collateral Amortized Cost	12,570	15,512
Agency Securities Pledged As Collateral Accrued Interest	36	45
Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	50,996	52,497
Agency Securities Pledged As Collateral Amortized Cost	52,482	52,899
Agency Securities Pledged As Collateral Accrued Interest	152	$ 153
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Securities Received as Collateral, Amount Repledged and Sold	$ 115

Pledged Assets (Assets Pledge49

Pledged Assets (Assets Pledged from Counterparties) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	$ 51,434	$ 53,055
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	10,352	10,467
Restricted Cash and Cash Equivalents	386	317
Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	247	82
Restricted Cash and Securities Pledged	10,959	10,935
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Securities Pledged	247	82
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	164	185
US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	10,712	10,853
Reverse Repurchase Agreements [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	10,712	10,853
Reverse Repurchase Agreements [Member] | US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	10,712	10,853
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	202	221
Restricted Cash and Cash Equivalents	331	281
Derivative [Member] | US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	49	72
Derivative [Member] | US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Available-for-sale Securities Pledged as Collateral	0	0
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	$ 247	$ 82

Pledged Assets (Offsetting Asse

Pledged Assets (Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Collateral Received	$ (3,407)
Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	11,180	$ 11,147
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	11,180	11,147
Financial Instruments	(7,608)	(9,705)
Collateral Received		(1,361)
Net Amount	165	81
Assets [Member] | ERROR in label resolution.
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	327	156
Net Amounts of Assets Presented in the Consolidated Balance Sheets	327	156
Financial Instruments	(1)	(1)
Collateral Received	(243)	(82)
Net Amount	83	73
Assets [Member] | TBA and Forward Settling Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	83	30
Net Amounts of Assets Presented in the Consolidated Balance Sheets	83	30
Financial Instruments	(1)	(22)
Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	48,958	50,324
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	48,958	50,324
Financial Instruments	(7,608)	(9,705)
Collateral Received	(41,350)	(40,619)
Net Amount	0
Liability [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Net Amount	0
Liability [Member] | ERROR in label resolution.
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	1	1
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1	1
Financial Instruments	(1)	(1)
Collateral Received	0	0
Net Amount	0	0
Liability [Member] | TBA and Forward Settling Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	1	27
Net Amounts of Assets Presented in the Consolidated Balance Sheets	1	27
Financial Instruments	(1)	(22)
Collateral Received	0	(5)
Net Amount	0	0
Reverse Repurchase Agreements [Member] | Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	10,770	10,961
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	10,770	10,961
Financial Instruments	(7,606)	(9,682)
Collateral Received	(3,164)	(1,279)
Repurchase Agreements [Member] | Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	48,956	50,296
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	48,956	50,296
Financial Instruments	(7,606)	(9,682)
Collateral Received	$ (41,350)	$ (40,614)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Future [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
TBA securities	$ 0	$ 19
Derivative Liability	30
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	153	75
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	174	81
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	1
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	$ 83	30
Transfers between hierarchy levels	0
Agency securities	$ 54,141	55,506
Agency securities transferred to consolidated VIEs	621	662
Non-Agency Securities, at Fair Value	36	36
Financial Instruments, Owned, Other, at Fair Value	884	876
U.S. Treasury securities	224	0
Marketable Securities, Equity Securities	42	29
TBA securities	410	205
Derivative Liability	32	28
Debt of consolidated variable interest entities, at fair value	336	357
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	10,352	10,467
Interest rate swaps	410	205
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	266	48
Total liabilities	10,352	10,467
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	56,092	57,266
Total liabilities	338	385
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Sale Of TBA And Forward Settling Agency Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability	$ 1	$ 27

Net Income (Loss) Per Common 52

Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic	391.3	331
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units	$ 0.2	$ 0.1
Weighted Average Number of Shares Outstanding, Diluted	391.5	331.1
Net Income (Loss) Available to Common Stockholders, Basic	$ 415	$ 69
Earnings Per Share, Basic and Diluted	$ 1.06	$ 0.21

Stockholders' Equity (Preferred

Stockholders' Equity (Preferred Stock) (Details) - USD ($) $ / shares in Units, $ in Millions	Sep. 12, 2017	Aug. 16, 2017	May 31, 2014	Mar. 31, 2018	Dec. 31, 2017	Dec. 31, 2012	May 05, 2014	Apr. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Document Period End Date				Mar. 31, 2018
Preferred Stock Authorized, but not Issued				10,000,000
Preferred Stock, Shares Authorized				10,000,000
Series A Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Dividend Rate, Percentage						8.00%
Preferred Stock, Liquidation Preference Per Share								$ 25
Payments for Repurchase of Redeemable Preferred Stock		$ 173
Series B Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Percent Interest Per Share			0.10%
Preferred Stock, Capital Shares Reserved for Future Issuance				8,050
Preferred Stock, Dividend Rate, Percentage					7.75%
Preferred Stock, Liquidation Preference Per Share	$ 25						$ 25
Preferred Stock, Shares Issued				7,000
Series C Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Capital Shares Reserved for Future Issuance				13,800
Preferred Stock, Dividend Rate, Percentage				5.111%	7.00%
Preferred Stock, Shares Issued				13,000	13,000
Proceeds from Issuance of Redeemable Preferred Stock	$ 315
Depositary Share [Member] | Series B Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Issued							7,000,000
Depositary Share [Member] | Series C Preferred Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Preferred Stock, Shares Issued	13,000,000

Stockholders' Equity (Accumulat

Stockholders' Equity (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	$ (621)	$ 46
Agency Securities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning OCI Balance	(345)	(397)
Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax	(620)	(38)
Amounts reclassified from accumulated OCI	(1)	84
Ending OCI Balance	$ (966)	$ (351)

Stockholders' Equity (Follow-On

Stockholders' Equity (Follow-On Equity Offerings) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Billions	Sep. 12, 2017	May 05, 2017	Mar. 31, 2018	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Document Period End Date			Mar. 31, 2018
Stock Issued During Period, Shares, New Issues	28.2	24.5		7.6
Stock Issued During Period, Value, New Issues	$ 1	$ 1		$ 0
Sale of Stock, Price Per Share	$ 20.47	$ 20.51		$ 20.96

Stockholders' Equity (At-the-Ma

Stockholders' Equity (At-the-Market Offering Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Sep. 12, 2017	May 05, 2017	Dec. 31, 2017	Mar. 31, 2018	Feb. 28, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, Value of Shares Approved for Future Issuance					$ 750
Common Stock, Shares Authorized				$ 589
Stock Issued During Period, Shares, New Issues	28.2	24.5	7.6
Stock Issued During Period, Value, New Issues	$ 1,000	$ 1,000	$ 0
Sale of Stock, Price Per Share	$ 20.47	$ 20.51	$ 20.96

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	May 02, 2018	Apr. 12, 2018	Sep. 12, 2017	May 05, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared					$ 0.54	$ 0.54
Stock Issued During Period, Shares, New Issues			28.2	24.5			7.6
Stock Issued During Period, Value, New Issues			$ 1,000,000	$ 1,000,000			$ 0
Subsequent Event [Member]
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared		$ 0.18
Gain (Loss) on Contract Termination	$ 0

Uncategorized Items - agnc-2018

Label	Element	Value
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	$ 1,282,000,000
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	$ 1,363,000,000