AGNC Investment (AGNC) 10-Q 5 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 26, 2018
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
Entity Registrant Name	AGNC Investment Corp.
Entity Central Index Key	1,423,689
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		477,831,997
Trading Symbol	AGNC

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Assets:
Agency securities, at fair value (including pledged securities of $67,889 and $53,055, respectively)	$ 70,408	$ 55,506
Agency securities transferred to consolidated variable interest entities, at fair value (pledged securities)	453	662
Credit risk transfer securities, at fair value (including pledged securities of $44 and $0, respectively)	997	876
Non-Agency securities, at fair value	507	36
U.S. Treasury securities, at fair value (including pledged securities of $45 and $0, respectively)	109	0
REIT equity securities, at fair value	0	29
Cash and cash equivalents	1,071	1,046
Restricted cash and cash equivalents	456	317
Derivative assets, at fair value	412	205
Receivable for investment securities sold (including pledged securities of $443 and $0, respectively)	524	0
Receivable under reverse repurchase agreements	16,309	10,961
Goodwill and other intangible assets, net	526	551
Other assets	259	187
Total assets	92,031	70,376
Liabilities:
Repurchase Agreements	65,734	50,296
Debt of consolidated variable interest entities, at fair value	291	357
Payable for investment securities purchased	23	95
Derivative liabilities, at fair value	62	28
Dividends payable	95	80
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	15,549	10,467
Accounts payable and other liabilities	650	299
Total liabilities	82,404	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; 900 and 600 shares authorized, respectively; 477.8 and 391.3 shares issued and outstanding, respectively	5	4
Additional paid-in capital	12,785	11,173
Retained deficit	(2,343)	(2,562)
Accumulated other comprehensive loss	(1,304)	(345)
Total stockholders' equity	9,627	8,754
Total liabilities and stockholders' equity	$ 92,031	$ 70,376

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parentheticals) - USD ($) shares in Millions, $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$ 68,109	$ 52,497
Preferred Stock B, Liquidation Preference, Value	175	175
Preferred Stock C, Liquidation Preference, Value	$ 325	$ 325
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Common Stock, Shares Authorized	900	600
Common Stock, Shares, Issued	477.8	391.3
Common Stock, Shares, Outstanding	477.8	391.3
Agency Securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$ 67,889	$ 53,055
Credit Risk Transfer Securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	44	0
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	0	0
US Treasury Securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	528	185
Receivable for securities sold [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	443	0
Asset Pledged as Collateral [Member] | US Treasury Securities [Member]
Financial Instruments Owned and Pledged as Collateral [Line Items]
Security Owned and Pledged as Collateral, Fair Value	$ 45	$ 0

Consolidated Statements Of Comp

Consolidated Statements Of Comprehensive Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Dividends declared per common share	$ 0.54	$ 0.54	$ 1.62	$ 1.62
Interest income:
Interest income	$ 500	$ 318	$ 1,345	$ 907
Interest expense	312	140	755	350
Net interest income	188	178	590	557
Other gain (loss), net:
Gain (loss) on sale of investment securities, net	(40)	22	(116)	(47)
Unrealized loss on investment securities measured at fair value through net income, net	(363)	(31)	(980)	(6)
Gain (loss) on derivative instruments and other securities, net	430	131	1,466	(78)
Management Fee Income	46	4	54	12
Total other gain (loss), net:	73	126	424	(119)
Expenses:
Compensation and benefits	14	10	34	30
Other operating expense	31	8	47	22
Total operating expense	45	18	81	52
Net income	216	286	933	386
Dividend on preferred stock	9	9	27	23
Issuance costs of redeemed preferred stock	0	6	0	6
Net income available to common stockholders	207	271	906	357
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	193	(90)	959	(257)
Comprehensive income (loss)	23	376	(26)	643
Comprehensive income (loss) available (attributable) to common stockholders	$ 14	$ 361	$ (53)	$ 614
Weighted average number of common shares outstanding - basic	462.3	364.7	419.8	347.5
Weighted average number of common shares outstanding - diluted	462.7	364.9	420.1	347.6
Net income per common share - basic	$ 0.45	$ 0.74	$ 2.16	$ 1.03
Net income per common share - diluted	$ 0.45	$ 0.74	$ 2.16	$ 1.03

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)	386			386
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	257				257
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	3		3
Proceeds from Issuance of Preferred Stock and Preference Stock	$ 315
Stock Redeemed or Called During Period, Shares	(167)
Issuance costs of redeemed preferred stock	$ (6)
Stock Issued During Period, Shares, New Issues		60.3
Stock Issued During Period, Value, New Issues	1,238	$ 1	1,237
Preferred dividends declared	(23)			23
Common dividends declared	(568)			(568)
Balance, value at Sep. 30, 2017	8,791	$ 4	11,172	(2,729)	(140)	0	169	315
Balance, Common Stock, shares at Sep. 30, 2017		391.3
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)	$ 933			933
Other comprehensive income (loss):
Unrealized Gains and (Losses), Net	(959)				(959)
Adjustments to Additional Paid in Capital, Share-based Compensation and Exercise of Stock Options	8		8
Proceeds from Issuance of Preferred Stock and Preference Stock	0
Issuance costs of redeemed preferred stock	0
Stock Issued During Period, Shares, New Issues		86.5
Stock Issued During Period, Value, New Issues	1,605	$ 1	1,604
Preferred dividends declared	(27)			(27)
Common dividends declared	(687)			(687)
Balance, value at Sep. 30, 2018	$ 9,627	$ 5	$ 12,785	$ (2,343)	$ (1,304)	$ 0	$ 169	$ 315
Balance, Common Stock, shares at Sep. 30, 2018	477.8	477.8

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Statement of Cash Flows [Abstract]
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 1,527	$ 1,392
Operating activities:
Net income (loss)	933	386
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of premiums and discounts on mortgage-backed securities, net	224	282
Amortization of intangible assets	25	3
Stock based compensation	5	3
Loss on sale of investment securities, net	116	47
Unrealized loss on investment securities measured at fair value through net income, net	980	6
(Gain) loss on derivative instruments and other securities, net	(1,466)	78
(Increase) decrease in other assets	(71)	99
Increase in accounts payable and other accrued liabilities	94	31
Net cash provided by operating activities	840	935
Investing activities:
Purchases of Agency mortgage-backed securities	(29,615)	(23,823)
Purchases of credit risk transfer and non-Agency securities	(1,051)	(881)
Proceeds from sale of Agency mortgage-backed securities	6,696	13,390
Proceeds from sale of credit risk transfer and non-Agency securities	483	437
Principal collections on Agency mortgage-backed securities	5,317	5,076
Principal collections on credit risk transfer and non-Agency securities	9	4
Payments on U.S. Treasury securities	(7,119)	(10,618)
Proceeds from U.S. Treasury securities	12,381	11,682
Net payments on reverse repurchase agreements	(5,175)	(1,456)
Net proceeds from derivative instruments	1,087	38
Net proceeds from (payments on) other investing activity	30	(4)
Net cash provided by investing activities	(16,957)	(6,155)
Financing activities:
Proceeds from repurchase arrangements	1,299,744	294,885
Payments on repurchase agreements	(1,284,306)	(287,238)
Payments on Federal Home Loan Bank advances	0	(3,037)
Payments on debt of consolidated variable interest entities	(63)	(80)
Net proceeds from preferred stock issuance	0	315
Payment for preferred stock redemption	0	(173)
Net proceeds from common stock issuances	1,605	1,238
Cash dividends paid	(699)	(580)
Net cash used in financing activities	16,281	5,330
Net change in cash and cash equivalents	164	$ 110
Cash and cash equivalents at end of period	$ 1,071

Unaudited Interim Consolidated

Unaudited Interim Consolidated Financial Statements	9 Months Ended
	Sep. 30, 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	9 Months Ended
	Sep. 30, 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 ("GSE") 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 GSE 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	9 Months Ended
	Sep. 30, 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. 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 securities pursuant to ASC Topic 825, Financial Instruments . 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. Consequently, all of our securities are reported at fair value on our consolidated balance sheet. 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 for which we elected the fair value option or are classified as trading 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. In our view, the election of the fair value option 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 derivative 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. 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 adjusted for credit impairments, 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 are considered to be at market. 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 registered central clearing exchanges and major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to economically hedge the variable cash flows associated with 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. 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 interest rate swaption agreements 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 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 of 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 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 use U.S. Treasury securities and U.S. Treasury futures contracts to mitigate the potential impact of changes in interest rates on the performance of our portfolio. We borrow U.S. Treasury securities under reverse repurchase agreements to cover short sales of U.S. Treasury securities. 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 U.S. Treasury security as of the reporting date. Gains and losses associated with 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. MTGE Management Agreement On May 2, 2018, MTGE announced its proposed sale to a third party. Coincident with the announcement, we entered into an amendment to our management agreement with MTGE. Pursuant to the amendment, we continued to manage MTGE through the closing of the proposed sale, which occurred on September 7, 2018, and for a one month transitional period following the closing. In addition to regular monthly management fees payable for ongoing service through the transition period, we were paid a termination fee under the management agreement of approximately $42 million , which is reported in management fee income in our consolidated statements of comprehensive income for the three and nine month periods ended September 30, 2018. Concurrent with the termination of the management agreement, we wrote-off the remaining unamortized intangible asset associated with the management agreement of approximately $23 million , which is reported in other operating expense in our consolidated statements of comprehensive income for the three and nine month periods ended September 30, 2018. 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 September 30, 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	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Investment Securities	3 years and ≤ 5 years 4,397 4,529 3.15% 2.42% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 50,933 52,655 3.92% 3.26% 45,977 46,398 3.75% 2.95% > 10 years 15,720 16,167 3.63% 3.36% 892 857 4.87% 4.74% Total $ 72,365 $ 74,691 3.82% 3.22% $ 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 September 30, 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 September 30, 2018 $ 7,641 $ (219 ) $ 16,855 $ (1,090 ) $ 24,496 $ (1,309 ) December 31, 2017 $ 3,582 $ (15 ) $ 20,577 $ (451 ) $ 24,159 $ (466 ) We did not recognize OTTI charges on our investment securities during the periods presented on our consolidated statements of operations. As of the end of each respective reporting period, a decision had not been made to sell 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 and nine months ended September 30, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended September 30, 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 $ (1,965 ) $ (1,039 ) $ (3,004 ) $ (3 ) $ (6,016 ) $ (6,019 ) Proceeds from investment securities sold 1 1,929 1,035 2,964 2 6,039 6,041 Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Gross gain on sale of investment securities $ 1 $ 2 $ 3 $ — $ 28 $ 28 Gross loss on sale of investment securities (37 ) (6 ) (43 ) (1 ) (5 ) (6 ) Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Nine Months Ended September 30, 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 $ (3,801 ) $ (4,017 ) $ (7,818 ) $ (5,738 ) $ (8,636 ) $ (14,374 ) Proceeds from investment securities sold 1 3,746 3,956 7,702 5,649 8,678 14,327 Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) Gross gain on sale of investment securities $ 6 $ 12 $ 18 $ 6 $ 48 $ 54 Gross loss on sale of investment securities (61 ) (73 ) (134 ) (95 ) (6 ) (101 ) Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) ________________________________ 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. Consolidated Variable Interest Entities As of September 30, 2018 and December 31, 2017 , our consolidated financial statements reflect the consolidation of certain variable interest entities ("VIEs") for which we have determined we are the primary beneficiary. The consolidated VIEs consist of CMO trusts 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 the 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." id="sjs-B4">Investment Securities As of September 30, 2018 and December 31, 2017 , our investment portfolio consisted of $72.4 billion and $57.1 billion of investment securities, at fair value, respectively, and $9.4 billion and $15.7 billion of TBA securities, at fair value, respectively. Our TBA position is reported at its net carrying value of $(43) million and $3 million as of September 30, 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 September 30, 2018 and December 31, 2017 , our investment securities had a net unamortized premium balance of $2.8 billion and $2.7 billion , respectively, including interest and principal-only securities. The following tables summarize our investment securities as of September 30, 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 . September 30, 2018 December 31, 2017 Investment Securities Amortized Cost Fair Value Amortized Fair Value Agency RMBS: Fixed rate $ 72,194 $ 69,844 $ 55,477 $ 55,026 Adjustable rate 229 230 278 283 CMO 623 609 629 631 Interest-only and principal-only strips 181 178 213 228 Total Agency RMBS 73,227 70,861 56,597 56,168 Non-Agency RMBS 375 374 7 7 CMBS 133 133 28 29 CRT securities 956 997 834 876 Total investment securities $ 74,691 $ 72,365 $ 57,466 $ 57,080 September 30, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 18,688 $ 5,987 $ 27 $ 7 $ — $ — $ 24,709 Unamortized discount (15 ) (2 ) — — — — (17 ) Unamortized premium 960 362 — — — — 1,322 Amortized cost 19,633 6,347 27 7 — — 26,014 Gross unrealized gains 3 1 1 — — — 5 Gross unrealized losses (960 ) (349 ) — — — — (1,309 ) Total available-for-sale securities, at fair value 18,676 5,999 28 7 — — 24,710 Securities remeasured at fair value through earnings: Par value 29,290 16,420 — 378 133 914 47,135 Unamortized discount (68 ) (2 ) — (10 ) (2 ) — (82 ) Unamortized premium 973 607 — — 2 42 1,624 Amortized cost 30,195 17,025 — 368 133 956 48,677 Gross unrealized gains 5 1 — — — 41 47 Gross unrealized losses (665 ) (403 ) — (1 ) — — (1,069 ) Total securities remeasured at fair value through earnings 29,535 16,623 — 367 133 997 47,655 Total securities, at fair value $ 48,211 $ 22,622 $ 28 $ 374 $ 133 $ 997 $ 72,365 Weighted average coupon as of September 30, 2018 3.77 % 3.84 % 3.24 % 3.85 % 4.49 % 5.76 % 3.82 % Weighted average yield as of September 30, 2018 1 3.16 % 3.23 % 2.04 % 4.16 % 4.71 % 5.64 % 3.22 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 6.8% based on forward rates as of September 30, 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 September 30, 2018 and December 31, 2017 , our investments in CRT and non-Agency securities had the following credit ratings: September 30, 2018 December 31, 2017 CRT and Non-Agency Security Credit Ratings 1 CRT RMBS CMBS CRT RMBS CMBS AAA $ — $ 276 $ 37 $ — $ 7 $ — AA — 21 61 — — — A 17 27 — 1 — — BBB 67 37 30 34 — 29 BB 428 8 5 370 — — B 458 2 — 455 — — Not Rated 27 3 — 16 — — Total $ 997 $ 374 $ 133 $ 876 $ 7 $ 29 ________________________________ 1. Represents the lowest of Standard and Poor's ("S&P"), Moody's, Fitch, DBRS, Kroll Bond Rating Agency ("KBRA") and Morningstar 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 September 30, 2018 , our CRT securities had floating and fixed rate coupons ranging from 3.6% to 9.2% , referenced to loans originated between 2011 and 2018 with weighted average coupons ranging from 3.6% to 4.5% . 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 September 30, 2018 and December 31, 2017 , the weighted average expected constant prepayment rate ("CPR") over the remaining life of our aggregate investment portfolio was 6.8% 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 September 30, 2018 and December 31, 2017 according to their estimated weighted average life classification (dollars in millions): September 30, 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 $ 1,315 $ 1,340 4.34% 2.67% $ 2,712 $ 2,693 3.90% 2.67% > 3 years and ≤ 5 years 4,397 4,529 3.15% 2.42% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 50,933 52,655 3.92% 3.26% 45,977 46,398 3.75% 2.95% > 10 years 15,720 16,167 3.63% 3.36% 892 857 4.87% 4.74% Total $ 72,365 $ 74,691 3.82% 3.22% $ 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 September 30, 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 September 30, 2018 $ 7,641 $ (219 ) $ 16,855 $ (1,090 ) $ 24,496 $ (1,309 ) December 31, 2017 $ 3,582 $ (15 ) $ 20,577 $ (451 ) $ 24,159 $ (466 ) We did not recognize OTTI charges on our investment securities during the periods presented on our consolidated statements of operations. As of the end of each respective reporting period, a decision had not been made to sell 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 and nine months ended September 30, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended September 30, 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 $ (1,965 ) $ (1,039 ) $ (3,004 ) $ (3 ) $ (6,016 ) $ (6,019 ) Proceeds from investment securities sold 1 1,929 1,035 2,964 2 6,039 6,041 Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Gross gain on sale of investment securities $ 1 $ 2 $ 3 $ — $ 28 $ 28 Gross loss on sale of investment securities (37 ) (6 ) (43 ) (1 ) (5 ) (6 ) Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Nine Months Ended September 30, 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 $ (3,801 ) $ (4,017 ) $ (7,818 ) $ (5,738 ) $ (8,636 ) $ (14,374 ) Proceeds from investment securities sold 1 3,746 3,956 7,702 5,649 8,678 14,327 Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) Gross gain on sale of investment securities $ 6 $ 12 $ 18 $ 6 $ 48 $ 54 Gross loss on sale of investment securities (61 ) (73 ) (134 ) (95 ) (6 ) (101 ) Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) ________________________________ 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. Consolidated Variable Interest Entities As of September 30, 2018 and December 31, 2017 , our consolidated financial statements reflect the consolidation of certain variable interest entities ("VIEs") for which we have determined we are the primary beneficiary. The consolidated VIEs consist of CMO trusts 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 the 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.

Repurchase Agreements And Other

Repurchase Agreements And Other Debt	9 Months Ended
	Sep. 30, 2018
Disclosure of Repurchase Agreements [Abstract]
Repurchase Agreements And Other Debt	1 to ≤ 3 months 16,273 2.30 % 56 16,150 1.50 % 50 > 3 to ≤ 6 months 9,472 2.15 % 110 7,287 1.50 % 130 > 6 to ≤ 9 months 400 2.78 % 254 2,361 1.66 % 225 > 9 to ≤ 12 months 700 2.53 % 279 202 1.64 % 297 > 12 to ≤ 24 months 2,099 2.78 % 486 1,700 1.84 % 468 > 24 to ≤ 36 months 925 2.79 % 829 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 65,684 2.30 % 67 $ 50,296 1.57 % 116 U.S.Treasury repo: > 1 day to ≤ 1 months 50 2.32 % 1 — — % — Total $ 65,734 2.30 % 67 $ 50,296 1.57 % 116 As of September 30, 2018 and December 31, 2017 , $14.0 billion and $5.3 billion , respectively, of our Agency repurchase agreements matured overnight and none of our repurchase agreements were due on demand. As of September 30, 2018 and December 31, 2017 , 39% and 33% , respectively, of our repurchase agreement funding was sourced through our wholly-owned captive broker-dealer subsidiary, Bethesda Securities, LLC ("BES"). Amounts sourced through BES include Agency repo funding from the General Collateral Finance Repo service ("GCF Repo") offered by the Fixed Income Clearing Corporation ("FICC"), which totaled 36% and 30% of our repurchase agreement funding outstanding as of September 30, 2018 and December 31, 2017 , respectively. Additionally, as of September 30, 2018 and December 31, 2017 , we had $3.9 billion and $2.7 billion , respectively, of U.S. Treasury reverse repurchase agreements sourced through BES with the FICC, which are reported in receivable under reverse repurchase agreements on our consolidated balance sheets." 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 September 30, 2018 , we had met all margin call requirements. For additional information regarding our pledged assets, please refer to Note 7 . Repurchase Agreements As of September 30, 2018 and December 31, 2017 , we had $65.7 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 September 30, 2018 and December 31, 2017 (dollars in millions): September 30, 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 $ 35,815 2.29 % 9 $ 19,771 1.59 % 11 > 1 to ≤ 3 months 16,273 2.30 % 56 16,150 1.50 % 50 > 3 to ≤ 6 months 9,472 2.15 % 110 7,287 1.50 % 130 > 6 to ≤ 9 months 400 2.78 % 254 2,361 1.66 % 225 > 9 to ≤ 12 months 700 2.53 % 279 202 1.64 % 297 > 12 to ≤ 24 months 2,099 2.78 % 486 1,700 1.84 % 468 > 24 to ≤ 36 months 925 2.79 % 829 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 65,684 2.30 % 67 $ 50,296 1.57 % 116 U.S.Treasury repo: > 1 day to ≤ 1 months 50 2.32 % 1 — — % — Total $ 65,734 2.30 % 67 $ 50,296 1.57 % 116 As of September 30, 2018 and December 31, 2017 , $14.0 billion and $5.3 billion , respectively, of our Agency repurchase agreements matured overnight and none of our repurchase agreements were due on demand. As of September 30, 2018 and December 31, 2017 , 39% and 33% , respectively, of our repurchase agreement funding was sourced through our wholly-owned captive broker-dealer subsidiary, Bethesda Securities, LLC ("BES"). Amounts sourced through BES include Agency repo funding from the General Collateral Finance Repo service ("GCF Repo") offered by the Fixed Income Clearing Corporation ("FICC"), which totaled 36% and 30% of our repurchase agreement funding outstanding as of September 30, 2018 and December 31, 2017 , respectively. Additionally, as of September 30, 2018 and December 31, 2017 , we had $3.9 billion and $2.7 billion , respectively, of U.S. Treasury reverse repurchase agreements sourced through BES with the FICC, which are reported in receivable under reverse repurchase agreements on our consolidated balance sheets.

Derivative and Other Hedging In

Derivative and Other Hedging Instruments	9 Months Ended
	Sep. 30, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
US Government Futures Securities [Table Text Block]	U.S. Treasury Futures September 30, 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 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,980 ) (1,960 ) 20 (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (1,650 ) $ (1,980 ) $ (1,960 ) $ 20 $ (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 September 30, 2018 and December 31, 2017 (in millions): Derivative and Other Hedging Instruments Balance Sheet Location September 30, 2018 December 31, 2017 Interest rate swaps Derivative assets, at fair value $ 217 $ 81 Swaptions Derivative assets, at fair value 157 75 TBA securities Derivative assets, at fair value 18 30 U.S. Treasury futures - short Derivative assets, at fair value 20 19 Total derivative assets, at fair value $ 412 $ 205 Interest rate swaps Derivative liabilities, at fair value $ (1 ) $ (1 ) TBA securities Derivative liabilities, at fair value (61 ) (27 ) Total derivative liabilities, at fair value $ (62 ) $ (28 ) U.S. Treasury securities - long U.S. Treasury securities, at fair value $ 109 $ — U.S. Treasury securities - short Obligation to return securities borrowed under reverse repurchase agreements, at fair value (15,549 ) (10,467 ) Total U.S. Treasury securities, net at fair value $ (15,440 ) $ (10,467 ) The following tables summarize certain characteristics of our derivative and other hedging instruments outstanding as of September 30, 2018 and December 31, 2017 (dollars in millions): September 30, 2018 December 31, 2017 Interest Rate Swaps Notional 1 Average Rate 2 Average Average Notional 1 Average Rate 2 Average Average ≤ 3 years $ 19,250 1.59% 2.33% 1.2 $ 21,025 1.40% 1.46% 1.5 > 3 to ≤ 5 years 9,975 1.96% 2.33% 3.9 6,825 1.82% 1.43% 4.1 > 5 to ≤ 7 years 5,025 2.54% 2.34% 6.1 5,775 2.02% 1.44% 5.9 > 7 to ≤ 10 years 10,000 2.33% 2.33% 8.5 6,650 2.10% 1.42% 9.1 > 10 years 4,425 2.59% 2.34% 11.8 3,425 2.49% 1.45% 12.9 Total $ 48,675 2.01% 2.33% 4.7 $ 43,700 1.74% 1.44% 4.5 ________________________________ 1. As of September 30, 2018 and December 31, 2017 , notional amount includes forward starting swaps of $4.9 billion and $4.6 billion , respectively, with an average forward start date of 0.5 and 0.3 years, respectively. 2. Average fixed pay rate includes forward starting swaps. Excluding forward starting swaps, the average fixed pay rate was 1.89% and 1.68% as of September 30, 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) September 30, 2018 ≤ 1 year $ 99 $ 127 4 $ 4,950 2.83% 3M 7.5 > 1 year ≤ 2 years 23 30 20 650 2.80% 3M 10.0 Total $ 122 $ 157 6 $ 5,600 2.83% 3M 7.8 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 September 30, 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 September 30, 2018 December 31, 2017 Maturity Face Amount (Short) Cost Basis 1 Fair Value Face Amount (Short) Cost Basis 1 Fair Value 5 years $ (230 ) $ (229 ) $ (228 ) $ (288 ) $ (286 ) $ (283 ) 7 years (10,319 ) (10,274 ) (9,989 ) (6,131 ) (6,106 ) (6,029 ) 10 years (5,554 ) (5,492 ) (5,223 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities $ (16,103 ) $ (15,995 ) $ (15,440 ) $ (10,699 ) $ (10,622 ) $ (10,467 ) ________________________________ 1. As of September 30, 2018 and December 31, 2017 , U.S. Treasury securities had a weighted average yield of 2.43% and 2.12% , respectively. U.S. Treasury Futures September 30, 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 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,980 ) (1,960 ) 20 (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (1,650 ) $ (1,980 ) $ (1,960 ) $ 20 $ (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. September 30, 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% $ 194 $ 190 $ 188 $ (2 ) $ 1,373 $ 1,372 $ 1,370 $ (2 ) 3.0% 567 565 560 (5 ) 3,161 3,225 3,217 (8 ) 3.5% 2,646 2,669 2,658 (11 ) 414 428 428 — 4.0% 1,224 1,250 1,248 (2 ) — — — — Total 15-Year TBA securities 4,631 4,674 4,654 (20 ) 4,948 5,025 5,015 (10 ) 30-Year TBA securities: 3.0% 843 812 805 (7 ) 4,317 4,303 4,312 9 3.5% (1,699 ) (1,683 ) (1,671 ) 12 3,932 4,027 4,034 7 4.0% 3,024 3,071 3,052 (19 ) 2,338 2,449 2,446 (3 ) 4.5% 2,475 2,562 2,553 (9 ) (61 ) (65 ) (65 ) — Total 30-Year TBA securities, net 4,643 4,762 4,739 (23 ) 10,526 10,714 10,727 13 Total TBA securities, net $ 9,274 $ 9,436 $ 9,393 $ (43 ) $ 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 and nine months ended September 30, 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 September 30, 2018: TBA securities, net $ 19,805 55,702 (66,233 ) $ 9,274 $ (56 ) Interest rate swaps $ 47,875 2,150 (1,350 ) $ 48,675 282 Payer swaptions $ 5,600 — — $ 5,600 30 U.S. Treasury securities - short position $ (13,394 ) (4,402 ) 1,583 $ (16,213 ) 150 U.S. Treasury securities - long position $ — 792 (682 ) $ 110 — U.S. Treasury futures contracts - short position $ (1,650 ) (1,650 ) 1,650 $ (1,650 ) 21 $ 427 Three months ended September 30, 2017: TBA securities, net $ 16,867 92,803 (90,792 ) $ 18,878 $ 158 Interest rate swaps $ 40,000 3,550 (1,400 ) $ 42,150 15 Payer swaptions $ 4,950 — — $ 4,950 (22 ) U.S. Treasury securities - short position $ (7,358 ) (5,105 ) 3,209 $ (9,254 ) (19 ) U.S. Treasury securities - long position $ — 1 (1 ) $ — — U.S. Treasury futures contracts - short position $ (2,910 ) (2,910 ) 2,910 $ (2,910 ) (1 ) $ 131 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 Nine months ended September 30, 2018: TBA securities, net $ 15,474 163,777 (169,977 ) $ 9,274 $ (362 ) Interest rate swaps $ 43,700 9,800 (4,825 ) $ 48,675 1,161 Payer swaptions $ 6,650 1,100 (2,150 ) $ 5,600 155 U.S. Treasury securities - short position $ (10,699 ) (10,693 ) 5,179 $ (16,213 ) 397 U.S. Treasury securities - long position $ — 1,841 (1,731 ) $ 110 — U.S. Treasury futures contracts - short position $ (2,910 ) (6,209 ) 7,469 $ (1,650 ) 104 $ 1,455 Nine months ended September 30, 2017: TBA securities, net $ 10,916 185,205 (177,243 ) $ 18,878 $ 360 Interest rate swaps $ 37,175 10,575 (5,600 ) $ 42,150 (157 ) Payer swaptions $ 1,200 3,750 — $ 4,950 (46 ) U.S. Treasury securities - short position $ (8,061 ) (11,595 ) 10,402 $ (9,254 ) (207 ) U.S. Treasury securities - long position $ 189 304 (493 ) $ — 1 U.S. Treasury futures contracts - short position $ (1,810 ) (8,430 ) 7,330 $ (2,910 ) (29 ) $ (78 ) ________________________________ 1. Amounts 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	9 Months Ended
	Sep. 30, 2018
Pledged Assets [Abstract]
Pledged Assets	30 and ≤ 60 days 9,512 9,728 29 12,950 13,061 38 > 60 and ≤ 90 days 7,774 8,017 25 4,000 4,013 11 > 90 days 14,187 14,742 44 15,385 15,512 45 Total RMBS $ 68,109 $ 70,379 $ 212 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $163 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of September 30, 2018 and December 31, 2017 , respectively. 2. September 30, 2018 amounts exclude $426 million of repledged U.S. Treasury securities received as collateral from counterparties. Assets Pledged from Counterparties As of September 30, 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). September 30, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 16,165 $ 80 $ 16,245 $ 10,853 $ — $ 10,853 Cash — 282 282 — 82 82 Total $ 16,165 $ 362 $ 16,527 $ 10,853 $ 82 $ 10,935 U.S Treasury securities received as collateral under our reverse repurchase agreements for which 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 September 30, 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 September 30, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 374 $ — $ 374 $ (1 ) $ (334 ) $ 39 TBA securities, at fair value 18 — 18 (18 ) — — Receivable under reverse repurchase agreements 16,309 — 16,309 (13,269 ) (3,036 ) 4 Total $ 16,701 $ — $ 16,701 $ (13,288 ) $ (3,370 ) $ 43 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 September 30, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 61 — 61 (18 ) (43 ) — Repurchase agreements 65,734 — 65,734 (13,269 ) (52,465 ) — Total $ 65,796 $ — $ 65,796 $ (13,288 ) $ (52,508 ) $ — 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. As of September 30, 2018 , our maximum amount at risk with any counterparty other than the Fixed Income Clearing Corporation related to our repurchase agreements was less than 4% of our tangible stockholders' equity. As of September 30, 2018 , approximately 8% of our tangible stockholder's equity was at risk with the Fixed Income Clearing Corporation. Equity at risk is defined as the net carrying value of securities pledged under repurchase agreements, including accrued interest plus any cash or assets on deposit to secure the repurchase obligation, less the amount of the repurchase liability, including accrued interest. 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 September 30, 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. 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 September 30, 2018 and December 31, 2017 (in millions): September 30, 2018 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 68,065 $ 453 $ 184 $ 246 $ 68,948 CRT - fair value 44 — — — 44 U.S. Treasury securities - fair value 3 470 — 58 — 528 Accrued interest on pledged securities 212 1 1 1 215 Restricted cash and cash equivalents 78 — 378 — 456 Total $ 68,869 $ 454 $ 621 $ 247 $ 70,191 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 $163 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of September 30, 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. 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. 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 September 30, 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 . September 30, 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 $ 36,636 $ 37,892 $ 114 $ 20,162 $ 20,313 $ 59 > 30 and ≤ 60 days 9,512 9,728 29 12,950 13,061 38 > 60 and ≤ 90 days 7,774 8,017 25 4,000 4,013 11 > 90 days 14,187 14,742 44 15,385 15,512 45 Total RMBS $ 68,109 $ 70,379 $ 212 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $163 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of September 30, 2018 and December 31, 2017 , respectively. 2. September 30, 2018 amounts exclude $426 million of repledged U.S. Treasury securities received as collateral from counterparties. Assets Pledged from Counterparties As of September 30, 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). September 30, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 16,165 $ 80 $ 16,245 $ 10,853 $ — $ 10,853 Cash — 282 282 — 82 82 Total $ 16,165 $ 362 $ 16,527 $ 10,853 $ 82 $ 10,935 U.S Treasury securities received as collateral under our reverse repurchase agreements for which 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 September 30, 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 September 30, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 374 $ — $ 374 $ (1 ) $ (334 ) $ 39 TBA securities, at fair value 18 — 18 (18 ) — — Receivable under reverse repurchase agreements 16,309 — 16,309 (13,269 ) (3,036 ) 4 Total $ 16,701 $ — $ 16,701 $ (13,288 ) $ (3,370 ) $ 43 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 September 30, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 61 — 61 (18 ) (43 ) — Repurchase agreements 65,734 — 65,734 (13,269 ) (52,465 ) — Total $ 65,796 $ — $ 65,796 $ (13,288 ) $ (52,508 ) $ — 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	9 Months Ended
	Sep. 30, 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 September 30, 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. September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Agency securities $ — $ 70,408 $ — $ — $ 55,506 $ — Agency securities transferred to consolidated VIEs — 453 — — 662 — Credit risk transfer securities — 997 — — 876 — Non-Agency securities — 507 — — 36 — U.S. Treasury securities 109 — — — — — REIT equity securities — — — 29 — — Interest rate swaps — 217 — — 81 — Swaptions — 157 — — 75 — TBA securities — 18 — — 30 — U.S. Treasury futures 20 — — 19 — — Total $ 129 $ 72,757 $ — $ 48 $ 57,266 $ — Liabilities: Debt of consolidated VIEs $ — $ 291 $ — $ — $ 357 $ — Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements 15,549 — — 10,467 — — Interest rate swaps — 1 — — 1 — TBA securities — 61 — — 27 — Total $ 15,549 $ 353 $ — $ 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)	9 Months Ended
	Sep. 30, 2018
Net Income (Loss) Per Common Share [Abstract]
Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]	Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted average number of common shares outstanding - basic 462.3 364.7 419.8 347.5 Unvested restricted stock units and performance share units 0.4 0.2 0.3 0.1 Weighted average number of common shares outstanding - diluted 462.7 364.9 420.1 347.6 Net income available to common stockholders $ 207 $ 271 $ 906 $ 357 Net income per common share - basic $ 0.45 $ 0.74 $ 2.16 $ 1.03 Net income per common share - diluted $ 0.45 $ 0.74 $ 2.16 $ 1.03
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 September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Weighted average number of common shares outstanding - basic 462.3 364.7 419.8 347.5 Unvested restricted stock units and performance share units 0.4 0.2 0.3 0.1 Weighted average number of common shares outstanding - diluted 462.7 364.9 420.1 347.6 Net income available to common stockholders $ 207 $ 271 $ 906 $ 357 Net income per common share - basic $ 0.45 $ 0.74 $ 2.16 $ 1.03 Net income per common share - diluted $ 0.45 $ 0.74 $ 2.16 $ 1.03

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 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 September 30, 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 September 30, 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 September 30, 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. Common Stock Offerings In May 2018, we completed a public offering in which 34.5 million shares of our common stock were sold to the underwriters for proceeds of $633 million , or $18.35 per common share, net of offering costs. In August 2018, we completed a follow-on public offering of 43.7 million shares of our common stock for proceeds of $817 million , or $18.68 per common share, net of estimated offering costs. 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 We have 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 a maximum aggregate offering price of our common stock. On June 14, 2018, our existing sales agreement terminated and we entered into new sales agreements for shares of our common stock having an aggregate offering price of up to $1 billion . During the three months ended September 30, 2018 , we did not sell any shares of our common stock under the sales agreements. During the nine months ended September 30, 2018 , we sold 8.3 million shares of our common stock under the sales agreements for proceeds of $155 million , or $18.73 per common share, net of offering costs. During the three and nine months ended September 30, 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 offering costs. As of September 30, 2018 , shares of our common stock with an aggregate offering price of $881 million remained available for issuance under this program. Accumulated Other Comprehensive Income (Loss) The following table summarizes changes to accumulated OCI for the three and nine months ended September 30, 2018 and 2017 (in millions): Three Months Ended September 30, Nine Months Ended September 30, Accumulated Other Comprehensive Income (Loss) 2018 2017 2018 2017 Beginning Balance $ (1,111 ) $ (230 ) $ (345 ) $ (397 ) OCI before reclassifications (229 ) 89 (1,014 ) 168 (Gain) loss amounts for available-for-sale securities reclassified from accumulated OCI to realized gain (loss) on sale of investment securities 36 1 55 89 Ending Balance $ (1,304 ) $ (140 ) $ (1,304 ) $ (140 )

Subsequent Event

Subsequent Event	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Event	Subsequent Events On October 11, 2018 , our Board of Directors declared a monthly dividend of $0.18 per common share, payable on November 9, 2018 to common stockholders of record as of October 31, 2018 .

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policy)	9 Months Ended
	Sep. 30, 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 are considered to be at market.
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. 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 securities pursuant to ASC Topic 825, Financial Instruments . 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. Consequently, all of our securities are reported at fair value on our consolidated balance sheet. 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 for which we elected the fair value option or are classified as trading 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. In our view, the election of the fair value option 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 derivative 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. 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 adjusted for credit impairments, 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 registered central clearing exchanges and major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to economically hedge the variable cash flows associated with 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. 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 interest rate swaption agreements 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 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 of 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 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 use U.S. Treasury securities and U.S. Treasury futures contracts to mitigate the potential impact of changes in interest rates on the performance of our portfolio. We borrow U.S. Treasury securities under reverse repurchase agreements to cover short sales of U.S. Treasury securities. 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 U.S. Treasury security as of the reporting date. Gains and losses associated with 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 September 30, 2018 , we did not accrue a loss contingency related to these matters.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 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 registered central clearing exchanges and major financial institutions with acceptable credit ratings, monitoring positions with individual counterparties and adjusting posted collateral as required. Interest rate swap agreements We use interest rate swaps to economically hedge the variable cash flows associated with 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. 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 interest rate swaption agreements 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 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 of 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 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 use U.S. Treasury securities and U.S. Treasury futures contracts to mitigate the potential impact of changes in interest rates on the performance of our portfolio. We borrow U.S. Treasury securities under reverse repurchase agreements to cover short sales of U.S. Treasury securities. 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 U.S. Treasury security as of the reporting date. Gains and losses associated with 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. 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 securities pursuant to ASC Topic 825, Financial Instruments . 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. Consequently, all of our securities are reported at fair value on our consolidated balance sheet. 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 for which we elected the fair value option or are classified as trading 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. In our view, the election of the fair value option 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 derivative 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. 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 adjusted for credit impairments, if any.
Management Agreement [Text Block]	MTGE Management Agreement On May 2, 2018, MTGE announced its proposed sale to a third party. Coincident with the announcement, we entered into an amendment to our management agreement with MTGE. Pursuant to the amendment, we continued to manage MTGE through the closing of the proposed sale, which occurred on September 7, 2018, and for a one month transitional period following the closing. In addition to regular monthly management fees payable for ongoing service through the transition period, we were paid a termination fee under the management agreement of approximately $42 million , which is reported in management fee income in our consolidated statements of comprehensive income for the three and nine month periods ended September 30, 2018. Concurrent with the termination of the management agreement, we wrote-off the remaining unamortized intangible asset associated with the management agreement of approximately $23 million , which is reported in other operating expense in our consolidated statements of comprehensive income for the three and nine month periods ended September 30, 2018.

Investment Securities (Tables)

Investment Securities (Tables)	9 Months Ended
	Sep. 30, 2018
Investments, Debt and Equity Securities [Abstract]
Securities by Credit Rating [Table Text Block]	As of September 30, 2018 and December 31, 2017 , our investments in CRT and non-Agency securities had the following credit ratings: September 30, 2018 December 31, 2017 CRT and Non-Agency Security Credit Ratings 1 CRT RMBS CMBS CRT RMBS CMBS AAA $ — $ 276 $ 37 $ — $ 7 $ — AA — 21 61 — — — A 17 27 — 1 — — BBB 67 37 30 34 — 29 BB 428 8 5 370 — — B 458 2 — 455 — — Not Rated 27 3 — 16 — — Total $ 997 $ 374 $ 133 $ 876 $ 7 $ 29 ________________________________ 1. Represents the lowest of Standard and Poor's ("S&P"), Moody's, Fitch, DBRS, Kroll Bond Rating Agency ("KBRA") and Morningstar credit ratings, stated in terms of the S&P equivalent rating as of each date.
Available-for-sale Securities [Table Text Block]	September 30, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 18,688 $ 5,987 $ 27 $ 7 $ — $ — $ 24,709 Unamortized discount (15 ) (2 ) — — — — (17 ) Unamortized premium 960 362 — — — — 1,322 Amortized cost 19,633 6,347 27 7 — — 26,014 Gross unrealized gains 3 1 1 — — — 5 Gross unrealized losses (960 ) (349 ) — — — — (1,309 ) Total available-for-sale securities, at fair value 18,676 5,999 28 7 — — 24,710 Securities remeasured at fair value through earnings: Par value 29,290 16,420 — 378 133 914 47,135 Unamortized discount (68 ) (2 ) — (10 ) (2 ) — (82 ) Unamortized premium 973 607 — — 2 42 1,624 Amortized cost 30,195 17,025 — 368 133 956 48,677 Gross unrealized gains 5 1 — — — 41 47 Gross unrealized losses (665 ) (403 ) — (1 ) — — (1,069 ) Total securities remeasured at fair value through earnings 29,535 16,623 — 367 133 997 47,655 Total securities, at fair value $ 48,211 $ 22,622 $ 28 $ 374 $ 133 $ 997 $ 72,365 Weighted average coupon as of September 30, 2018 3.77 % 3.84 % 3.24 % 3.85 % 4.49 % 5.76 % 3.82 % Weighted average yield as of September 30, 2018 1 3.16 % 3.23 % 2.04 % 4.16 % 4.71 % 5.64 % 3.22 % ________________________________ 1. Incorporates a weighted average future constant prepayment rate assumption of 6.8% based on forward rates as of September 30, 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 .
Components of Investment Securities	The following tables summarize our investment securities as of September 30, 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 . September 30, 2018 December 31, 2017 Investment Securities Amortized Cost Fair Value Amortized Fair Value Agency RMBS: Fixed rate $ 72,194 $ 69,844 $ 55,477 $ 55,026 Adjustable rate 229 230 278 283 CMO 623 609 629 631 Interest-only and principal-only strips 181 178 213 228 Total Agency RMBS 73,227 70,861 56,597 56,168 Non-Agency RMBS 375 374 7 7 CMBS 133 133 28 29 CRT securities 956 997 834 876 Total investment securities $ 74,691 $ 72,365 $ 57,466 $ 57,080 September 30, 2018 Agency RMBS Non-Agency Investment Securities Fannie Mae Freddie Mac Ginnie Mae RMBS CMBS CRT Total Available-for-sale securities: Par value $ 18,688 $ 5,987 $ 27 $ 7 $ — $ — $ 24,709 Unamortized discount (15 ) (2 ) — — — — (17 ) Unamortized premium 960 362 — — — — 1,322 Amortized cost 19,633 6,347 27 7 — — 26,014 Gross unrealized gains 3 1 1 — — — 5 Gross unrealized losses (960 ) (349 ) — — — — (1,309 ) Total available-for-sale securities, at fair value 18,676 5,999 28 7 — — 24,710 Securities remeasured at fair value through earnings: Par value 29,290 16,420 — 378 133 914 47,135 Unamortized discount (68 ) (2 ) — (10 ) (2 ) — (82 ) Unamortized premium 973 607 — — 2 42 1,624 Amortized cost 30,195 17,025 — 368 133 956 48,677 Gross unrealized gains 5 1 — — — 41 47 Gross unrealized losses (665 ) (403 ) — (1 ) — — (1,069 ) Total securities remeasured at fair value through earnings 29,535 16,623 — 367 133 997 47,655 Total securities, at fair value $ 48,211 $ 22,622 $ 28 $ 374 $ 133 $ 997 $ 72,365 Weighted average coupon as of September 30, 2018 3.77 % 3.84 % 3.24 % 3.85 % 4.49 % 5.76 % 3.82 % Weighted average yield as of September 30, 2018 1 3.16 % 3.23 % 2.04 % 4.16 % 4.71 % 5.64 % 3.22 %
Summary Of Agency Securities Estimated Weighted Average Life Classifications	The following table summarizes our investments as of September 30, 2018 and December 31, 2017 according to their estimated weighted average life classification (dollars in millions): September 30, 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 $ 1,315 $ 1,340 4.34% 2.67% $ 2,712 $ 2,693 3.90% 2.67% > 3 years and ≤ 5 years 4,397 4,529 3.15% 2.42% 7,499 7,518 3.31% 2.39% > 5 years and ≤10 years 50,933 52,655 3.92% 3.26% 45,977 46,398 3.75% 2.95% > 10 years 15,720 16,167 3.63% 3.36% 892 857 4.87% 4.74% Total $ 72,365 $ 74,691 3.82% 3.22% $ 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 September 30, 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 September 30, 2018 $ 7,641 $ (219 ) $ 16,855 $ (1,090 ) $ 24,496 $ (1,309 ) 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 and nine months ended September 30, 2018 and 2017 by investment classification of accounting (in millions): Three Months Ended September 30, 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 $ (1,965 ) $ (1,039 ) $ (3,004 ) $ (3 ) $ (6,016 ) $ (6,019 ) Proceeds from investment securities sold 1 1,929 1,035 2,964 2 6,039 6,041 Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Gross gain on sale of investment securities $ 1 $ 2 $ 3 $ — $ 28 $ 28 Gross loss on sale of investment securities (37 ) (6 ) (43 ) (1 ) (5 ) (6 ) Net gain (loss) on sale of investment securities $ (36 ) $ (4 ) $ (40 ) $ (1 ) $ 23 $ 22 Nine Months Ended September 30, 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 $ (3,801 ) $ (4,017 ) $ (7,818 ) $ (5,738 ) $ (8,636 ) $ (14,374 ) Proceeds from investment securities sold 1 3,746 3,956 7,702 5,649 8,678 14,327 Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) Gross gain on sale of investment securities $ 6 $ 12 $ 18 $ 6 $ 48 $ 54 Gross loss on sale of investment securities (61 ) (73 ) (134 ) (95 ) (6 ) (101 ) Net gain (loss) on sale of investment securities $ (55 ) $ (61 ) $ (116 ) $ (89 ) $ 42 $ (47 ) ________________________________ 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 Oth_2

Repurchase Agreements and Other Debt (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017 (dollars in millions): September 30, 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 $ 35,815 2.29 % 9 $ 19,771 1.59 % 11 > 1 to ≤ 3 months 16,273 2.30 % 56 16,150 1.50 % 50 > 3 to ≤ 6 months 9,472 2.15 % 110 7,287 1.50 % 130 > 6 to ≤ 9 months 400 2.78 % 254 2,361 1.66 % 225 > 9 to ≤ 12 months 700 2.53 % 279 202 1.64 % 297 > 12 to ≤ 24 months 2,099 2.78 % 486 1,700 1.84 % 468 > 24 to ≤ 36 months 925 2.79 % 829 2,200 1.80 % 803 > 36 to ≤ 48 months — — % — 625 1.90 % 1,141 Total Agency repo $ 65,684 2.30 % 67 $ 50,296 1.57 % 116 U.S.Treasury repo: > 1 day to ≤ 1 months 50 2.32 % 1 — — % — Total $ 65,734 2.30 % 67 $ 50,296 1.57 % 116

Derivative and Other Hedging _2

Derivative and Other Hedging Instruments (Tables)	9 Months Ended
	Sep. 30, 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 September 30, 2018 and December 31, 2017 (in millions): Derivative and Other Hedging Instruments Balance Sheet Location September 30, 2018 December 31, 2017 Interest rate swaps Derivative assets, at fair value $ 217 $ 81 Swaptions Derivative assets, at fair value 157 75 TBA securities Derivative assets, at fair value 18 30 U.S. Treasury futures - short Derivative assets, at fair value 20 19 Total derivative assets, at fair value $ 412 $ 205 Interest rate swaps Derivative liabilities, at fair value $ (1 ) $ (1 ) TBA securities Derivative liabilities, at fair value (61 ) (27 ) Total derivative liabilities, at fair value $ (62 ) $ (28 ) U.S. Treasury securities - long U.S. Treasury securities, at fair value $ 109 $ — U.S. Treasury securities - short Obligation to return securities borrowed under reverse repurchase agreements, at fair value (15,549 ) (10,467 ) Total U.S. Treasury securities, net at fair value $ (15,440 ) $ (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) September 30, 2018 ≤ 1 year $ 99 $ 127 4 $ 4,950 2.83% 3M 7.5 > 1 year ≤ 2 years 23 30 20 650 2.80% 3M 10.0 Total $ 122 $ 157 6 $ 5,600 2.83% 3M 7.8 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 September 30, 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 September 30, 2018 December 31, 2017 Maturity Face Amount (Short) Cost Basis 1 Fair Value Face Amount (Short) Cost Basis 1 Fair Value 5 years $ (230 ) $ (229 ) $ (228 ) $ (288 ) $ (286 ) $ (283 ) 7 years (10,319 ) (10,274 ) (9,989 ) (6,131 ) (6,106 ) (6,029 ) 10 years (5,554 ) (5,492 ) (5,223 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities $ (16,103 ) $ (15,995 ) $ (15,440 ) $ (10,699 ) $ (10,622 ) $ (10,467 )
US government securities	U.S. Treasury Securities September 30, 2018 December 31, 2017 Maturity Face Amount (Short) Cost Basis 1 Fair Value Face Amount (Short) Cost Basis 1 Fair Value 5 years $ (230 ) $ (229 ) $ (228 ) $ (288 ) $ (286 ) $ (283 ) 7 years (10,319 ) (10,274 ) (9,989 ) (6,131 ) (6,106 ) (6,029 ) 10 years (5,554 ) (5,492 ) (5,223 ) (4,280 ) (4,230 ) (4,155 ) Total U.S. Treasury securities $ (16,103 ) $ (15,995 ) $ (15,440 ) $ (10,699 ) $ (10,622 ) $ (10,467 )
US Government Futures Securities [Table Text Block]	U.S. Treasury Futures September 30, 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 ) $ (852 ) $ (848 ) $ 4 10 years (1,650 ) (1,980 ) (1,960 ) 20 (2,180 ) (2,718 ) (2,703 ) 15 Total U.S. Treasury futures $ (1,650 ) $ (1,980 ) $ (1,960 ) $ 20 $ (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	September 30, 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% $ 194 $ 190 $ 188 $ (2 ) $ 1,373 $ 1,372 $ 1,370 $ (2 ) 3.0% 567 565 560 (5 ) 3,161 3,225 3,217 (8 ) 3.5% 2,646 2,669 2,658 (11 ) 414 428 428 — 4.0% 1,224 1,250 1,248 (2 ) — — — — Total 15-Year TBA securities 4,631 4,674 4,654 (20 ) 4,948 5,025 5,015 (10 ) 30-Year TBA securities: 3.0% 843 812 805 (7 ) 4,317 4,303 4,312 9 3.5% (1,699 ) (1,683 ) (1,671 ) 12 3,932 4,027 4,034 7 4.0% 3,024 3,071 3,052 (19 ) 2,338 2,449 2,446 (3 ) 4.5% 2,475 2,562 2,553 (9 ) (61 ) (65 ) (65 ) — Total 30-Year TBA securities, net 4,643 4,762 4,739 (23 ) 10,526 10,714 10,727 13 Total TBA securities, net $ 9,274 $ 9,436 $ 9,393 $ (43 ) $ 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 and nine months ended September 30, 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 September 30, 2018: TBA securities, net $ 19,805 55,702 (66,233 ) $ 9,274 $ (56 ) Interest rate swaps $ 47,875 2,150 (1,350 ) $ 48,675 282 Payer swaptions $ 5,600 — — $ 5,600 30 U.S. Treasury securities - short position $ (13,394 ) (4,402 ) 1,583 $ (16,213 ) 150 U.S. Treasury securities - long position $ — 792 (682 ) $ 110 — U.S. Treasury futures contracts - short position $ (1,650 ) (1,650 ) 1,650 $ (1,650 ) 21 $ 427 Three months ended September 30, 2017: TBA securities, net $ 16,867 92,803 (90,792 ) $ 18,878 $ 158 Interest rate swaps $ 40,000 3,550 (1,400 ) $ 42,150 15 Payer swaptions $ 4,950 — — $ 4,950 (22 ) U.S. Treasury securities - short position $ (7,358 ) (5,105 ) 3,209 $ (9,254 ) (19 ) U.S. Treasury securities - long position $ — 1 (1 ) $ — — U.S. Treasury futures contracts - short position $ (2,910 ) (2,910 ) 2,910 $ (2,910 ) (1 ) $ 131 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 Nine months ended September 30, 2018: TBA securities, net $ 15,474 163,777 (169,977 ) $ 9,274 $ (362 ) Interest rate swaps $ 43,700 9,800 (4,825 ) $ 48,675 1,161 Payer swaptions $ 6,650 1,100 (2,150 ) $ 5,600 155 U.S. Treasury securities - short position $ (10,699 ) (10,693 ) 5,179 $ (16,213 ) 397 U.S. Treasury securities - long position $ — 1,841 (1,731 ) $ 110 — U.S. Treasury futures contracts - short position $ (2,910 ) (6,209 ) 7,469 $ (1,650 ) 104 $ 1,455 Nine months ended September 30, 2017: TBA securities, net $ 10,916 185,205 (177,243 ) $ 18,878 $ 360 Interest rate swaps $ 37,175 10,575 (5,600 ) $ 42,150 (157 ) Payer swaptions $ 1,200 3,750 — $ 4,950 (46 ) U.S. Treasury securities - short position $ (8,061 ) (11,595 ) 10,402 $ (9,254 ) (207 ) U.S. Treasury securities - long position $ 189 304 (493 ) $ — 1 U.S. Treasury futures contracts - short position $ (1,810 ) (8,430 ) 7,330 $ (2,910 ) (29 ) $ (78 ) ________________________________ 1. Amounts 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 September 30, 2018 and December 31, 2017 (dollars in millions): September 30, 2018 December 31, 2017 Interest Rate Swaps Notional 1 Average Rate 2 Average Average Notional 1 Average Rate 2 Average Average ≤ 3 years $ 19,250 1.59% 2.33% 1.2 $ 21,025 1.40% 1.46% 1.5 > 3 to ≤ 5 years 9,975 1.96% 2.33% 3.9 6,825 1.82% 1.43% 4.1 > 5 to ≤ 7 years 5,025 2.54% 2.34% 6.1 5,775 2.02% 1.44% 5.9 > 7 to ≤ 10 years 10,000 2.33% 2.33% 8.5 6,650 2.10% 1.42% 9.1 > 10 years 4,425 2.59% 2.34% 11.8 3,425 2.49% 1.45% 12.9 Total $ 48,675 2.01% 2.33% 4.7 $ 43,700 1.74% 1.44% 4.5

Pledged Assets (Tables)

Pledged Assets (Tables)	9 Months Ended
	Sep. 30, 2018
Pledged Assets [Abstract]
Schedule of Securities and Cash Pledged as Collateral from Counterparties [Table Text Block]	As of September 30, 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). September 30, 2018 December 31, 2017 Assets Pledged to AGNC Reverse Repurchase Agreements Derivative Agreements Total Reverse Repurchase Agreements Derivative Agreements Total U.S. Treasury securities - fair value $ 16,165 $ 80 $ 16,245 $ 10,853 $ — $ 10,853 Cash — 282 282 — 82 82 Total $ 16,165 $ 362 $ 16,527 $ 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 September 30, 2018 and December 31, 2017 (in millions): September 30, 2018 Assets Pledged to Counterparties Repurchase Agreements 1 Debt of Consolidated VIEs Derivative Agreements Prime Broker Agreements 2 Total Agency RMBS - fair value $ 68,065 $ 453 $ 184 $ 246 $ 68,948 CRT - fair value 44 — — — 44 U.S. Treasury securities - fair value 3 470 — 58 — 528 Accrued interest on pledged securities 212 1 1 1 215 Restricted cash and cash equivalents 78 — 378 — 456 Total $ 68,869 $ 454 $ 621 $ 247 $ 70,191 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 $163 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of September 30, 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 September 30, 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 . September 30, 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 $ 36,636 $ 37,892 $ 114 $ 20,162 $ 20,313 $ 59 > 30 and ≤ 60 days 9,512 9,728 29 12,950 13,061 38 > 60 and ≤ 90 days 7,774 8,017 25 4,000 4,013 11 > 90 days 14,187 14,742 44 15,385 15,512 45 Total RMBS $ 68,109 $ 70,379 $ 212 $ 52,497 $ 52,899 $ 153 ________________________________ 1. Includes $163 million and $182 million of retained interests in our consolidated VIEs pledged as collateral under repurchase agreements as of September 30, 2018 and December 31, 2017 , respectively. 2. September 30, 2018 amounts exclude $426 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 September 30, 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 September 30, 2018 Interest rate swap and swaption agreements, at fair value 1 $ 374 $ — $ 374 $ (1 ) $ (334 ) $ 39 TBA securities, at fair value 18 — 18 (18 ) — — Receivable under reverse repurchase agreements 16,309 — 16,309 (13,269 ) (3,036 ) 4 Total $ 16,701 $ — $ 16,701 $ (13,288 ) $ (3,370 ) $ 43 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 September 30, 2018 Interest rate swap agreements, at fair value 1 $ 1 $ — $ 1 $ (1 ) $ — $ — TBA securities, at fair value 61 — 61 (18 ) (43 ) — Repurchase agreements 65,734 — 65,734 (13,269 ) (52,465 ) — Total $ 65,796 $ — $ 65,796 $ (13,288 ) $ (52,508 ) $ — 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)	9 Months Ended
	Sep. 30, 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 September 30, 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. September 30, 2018 December 31, 2017 Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Agency securities $ — $ 70,408 $ — $ — $ 55,506 $ — Agency securities transferred to consolidated VIEs — 453 — — 662 — Credit risk transfer securities — 997 — — 876 — Non-Agency securities — 507 — — 36 — U.S. Treasury securities 109 — — — — — REIT equity securities — — — 29 — — Interest rate swaps — 217 — — 81 — Swaptions — 157 — — 75 — TBA securities — 18 — — 30 — U.S. Treasury futures 20 — — 19 — — Total $ 129 $ 72,757 $ — $ 48 $ 57,266 $ — Liabilities: Debt of consolidated VIEs $ — $ 291 $ — $ — $ 357 $ — Obligation to return U.S. Treasury securities borrowed under reverse repurchase agreements 15,549 — — 10,467 — — Interest rate swaps — 1 — — 1 — TBA securities — 61 — — 27 — Total $ 15,549 $ 353 $ — $ 10,467 $ 385 $ —

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following table summarizes changes to accumulated OCI for the three and nine months ended September 30, 2018 and 2017 (in millions): Three Months Ended September 30, Nine Months Ended September 30, Accumulated Other Comprehensive Income (Loss) 2018 2017 2018 2017 Beginning Balance $ (1,111 ) $ (230 ) $ (345 ) $ (397 ) OCI before reclassifications (229 ) 89 (1,014 ) 168 (Gain) loss amounts for available-for-sale securities reclassified from accumulated OCI to realized gain (loss) on sale of investment securities 36 1 55 89 Ending Balance $ (1,304 ) $ (140 ) $ (1,304 ) $ (140 )

Organization (Details)

Organization (Details)	9 Months Ended
	Sep. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Required Annual Distribution of Taxable Net Income	90.00%
Intended annual distribution of taxable net income	100.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	May 02, 2018	Sep. 30, 2018
Derivative [Line Items]
Gain (Loss) on Contract Termination	$ 41,700
Document Period End Date		Sep. 30, 2018
Required Annual Distribution of Taxable Net Income		90.00%
Indefinite-lived Intangible Assets, Written off Related to Sale of Business Unit		$ 23,000

Investment Securities (Narrativ

Investment Securities (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Sep. 30, 2018
Mortgage-backed Securities Available-for-sale, Fair Value Disclosure	$ 72,365	$ 57,080
Weighted average expected constant prepayment rate	7.00%	8.00%
Variable Interest Entity, Consolidated, Carrying Amount, Assets	$ (453)	$ (662)
Debt, at fair value	(291)	(357)
Agency Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Unamortized premium balance	2,800	2,700
TBA securities Fifteen Year and Thirty Year Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Net long TBA position, at fair value	9,400	15,700
TBA, net carrying value	$ (43)	$ 3
Credit Risk Transfer Securities [Member] | Minimum [Member]
Debt Securities, Available-for-sale [Line Items]
Weighted Average Coupon Rate	3.60%	3.90%
Underlying Collateral Coupon	3.60%	3.60%
Credit Risk Transfer Securities [Member] | Maximum [Member]
Debt Securities, Available-for-sale [Line Items]
Weighted Average Coupon Rate	9.20%	8.50%
Underlying Collateral Coupon	4.50%	4.40%

Investment Securities (Summary

Investment Securities (Summary of Investment in Agency Security) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	$ 74,691	$ 57,466
Document Period End Date	Sep. 30, 2018
Debt Securities, Trading and Available-for-sale	$ 72,365	57,080
Total agency MBS, at fair value	70,861	56,168
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	375	7
Debt Securities, Trading and Available-for-sale	374	7
Commercial Mortgage Backed Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	133	28
Debt Securities, Trading and Available-for-sale	133	29
Credit Risk Transfer Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	956	834
Debt Securities, Trading and Available-for-sale	997	876
Fixed Income Securities [Member] | Agency Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	72,194	55,477
Debt Securities, Trading and Available-for-sale	69,844	55,026
Adjustable-Rate [Member] | Agency Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	229	278
Debt Securities, Trading and Available-for-sale	230	283
Collateralized Mortgage Obligations [Member] | Agency Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	623	629
Debt Securities, Trading and Available-for-sale	609	631
Interest Only And Principal Only Strip [Member] | Agency Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	181	213
Debt Securities, Trading and Available-for-sale	178	228
Agency Securities [Member]
Debt Securities, Trading and Available-for-sale, Amortized Cost Basis	$ 73,227	$ 56,597

Investment Securities (Componen

Investment Securities (Components Of Investment Securities) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Schedule of Investments [Line Items]
Document Period End Date	Sep. 30, 2018
Agency securities transferred to consolidated VIEs	$ 453	$ 662
Debt Securities, Trading	47,655	23,427
Debt Securities, Trading and Available-for-sale	72,365	57,080
Amortized cost	$ 74,691	$ 57,466
Weighted average coupon	3.82%	3.71%
Weighted average yield	3.22%	2.89%
Future Prepayment Rate Assumption Of Investment Portfolio	7.00%	8.00%
Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 24,709	$ 32,460
Unamortized discount	(17)	(28)
Unamortized premium	1,322	1,566
Amortized cost	26,014	33,998
Gross unrealized gains	5	121
Gross unrealized losses	(1,309)	(466)
Total available-for-sale securities, at fair value	24,710	33,653
Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	(82)	(35)
Unamortized premium	1,624	1,159
Debt Securities, Trading, Unrealized Gain	47	71
Debt Securities, Trading, Unrealized Loss	1,069	112
Trading Securities, Cost	48,677	23,468
Trading Securities Par	47,135	22,344
Fannie Mae [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	29,535	14,191
Debt Securities, Trading and Available-for-sale	$ 48,211	$ 39,258
Weighted average coupon	3.77%	3.67%
Weighted average yield	3.16%	2.84%
Fannie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 18,688	$ 24,200
Unamortized discount	(15)	(25)
Unamortized premium	960	1,119
Amortized cost	19,633	25,294
Gross unrealized gains	3	98
Gross unrealized losses	(960)	(325)
Total available-for-sale securities, at fair value	18,676	25,067
Fannie Mae [Member] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	(68)	(34)
Unamortized premium	973	711
Debt Securities, Trading, Unrealized Gain	5	26
Debt Securities, Trading, Unrealized Loss	665	70
Trading Securities, Cost	30,195	14,235
Trading Securities Par	29,290	13,558
Freddie Mac [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	16,623	8,331
Debt Securities, Trading and Available-for-sale	$ 22,622	$ 16,875
Weighted average coupon	3.84%	3.73%
Weighted average yield	3.23%	2.87%
Freddie Mac [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 5,987	$ 8,219
Unamortized discount	(2)	(3)
Unamortized premium	362	447
Amortized cost	6,347	8,663
Gross unrealized gains	1	22
Gross unrealized losses	(349)	(141)
Total available-for-sale securities, at fair value	5,999	8,544
Freddie Mac [Member] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	(2)	0
Unamortized premium	607	415
Debt Securities, Trading, Unrealized Gain	1	2
Debt Securities, Trading, Unrealized Loss	403	42
Trading Securities, Cost	17,025	8,371
Trading Securities Par	16,420	7,956
Ginnie Mae [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	0	0
Debt Securities, Trading and Available-for-sale	$ 28	$ 35
Weighted average coupon	3.24%	2.84%
Weighted average yield	2.04%	2.02%
Ginnie Mae [Member] | Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Par value	$ 27	$ 34
Unamortized discount	0	0
Unamortized premium	0	0
Amortized cost	27	34
Gross unrealized gains	1	1
Gross unrealized losses	0	0
Total available-for-sale securities, at fair value	28	35
Ginnie Mae [Member] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	0	0
Unamortized premium	0	0
Debt Securities, Trading, Unrealized Gain	0	0
Debt Securities, Trading, Unrealized Loss	0	0
Trading Securities, Cost	0	0
Trading Securities Par	0	0
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	367	0
Debt Securities, Trading and Available-for-sale	$ 374	$ 7
Weighted average coupon	3.85%	2.50%
Weighted average yield	4.16%	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] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	(10)	0
Unamortized premium	0	0
Debt Securities, Trading, Unrealized Gain	0	0
Debt Securities, Trading, Unrealized Loss	1	0
Trading Securities, Cost	368	0
Trading Securities Par	378	0
Commercial Mortgage Backed Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	133	29
Debt Securities, Trading and Available-for-sale	$ 133	$ 29
Weighted average coupon	4.49%	6.55%
Weighted average yield	4.71%	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] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	(2)	(1)
Unamortized premium	2	0
Debt Securities, Trading, Unrealized Gain	0	1
Debt Securities, Trading, Unrealized Loss	0	0
Trading Securities, Cost	133	28
Trading Securities Par	133	29
Credit Risk Transfer Securities [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading	997	876
Debt Securities, Trading and Available-for-sale	$ 997	$ 876
Weighted average coupon	5.76%	5.26%
Weighted average yield	5.64%	5.19%
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] | Trading Securities [Member]
Schedule of Investments [Line Items]
Unamortized discount	0	0
Unamortized premium	42	33
Debt Securities, Trading, Unrealized Gain	41	42
Debt Securities, Trading, Unrealized Loss	0	0
Trading Securities, Cost	956	834
Trading Securities Par	914	801
Credit Risk Transfer Securities [Member] | Securities Remeasured at Fair Value [Member]
Schedule of Investments [Line Items]
Debt Securities, Trading and Available-for-sale	$ 997	$ 876

Investment Securities (Summar_2

Investment Securities (Summary Of Agency Securities Estimated Weighted Average Life Classifications) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Document Period End Date	Sep. 30, 2018
Agency securities classified as available for sale, Fair value	$ 72,365	$ 57,080
Agency securities classified as available for sale, Amortized cost	$ 74,691	$ 57,466
Weighted Average Coupon	3.82%	3.71%
Weighted Average Yield	3.22%	2.89%
Greater Than One Year and Less Than or Equal to Three Years [Member]
Fair Value	$ 1,315	$ 2,712
Amortized Cost	$ 1,340	$ 2,693
Weighted Average Coupon	4.34%	3.90%
Weighted Average Yield	2.67%	2.67%
Greater Than Three Years and Less Than or Equal to Five Years [Member]
Fair Value	$ 4,397	$ 7,499
Amortized Cost	$ 4,529	$ 7,518
Weighted Average Coupon	3.15%	3.31%
Weighted Average Yield	2.42%	2.39%
Greater Than Five Years [Member]
Fair Value	$ 50,933	$ 45,977
Amortized Cost	$ 52,655	$ 46,398
Weighted Average Coupon	3.92%	3.75%
Weighted Average Yield	3.26%	2.95%
Greater Than Ten Years [Member]
Fair Value	$ 15,720	$ 892
Amortized Cost	$ 16,167	$ 857
Weighted Average Coupon	3.63%	4.87%
Weighted Average Yield	3.36%	4.74%

Investment Securities (Summar_3

Investment Securities (Summary Of Changes In Accumulated OCI For Available-For-Sale Security) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Unrealized Gains and (Losses), Net	$ (193)	$ 90	$ (959)	$ 257
Agency Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning OCI Balance	(1,111)	(230)	(345)	(397)
Unrealized Gains and (Losses), Net	(229)	89	(1,014)	168
Reversal of Unrealized (Gains) and Losses, Net on Realization	36	1	55	89
Ending OCI Balance	$ (1,304)	$ (140)	$ (1,304)	$ (140)

Investment Securities (Summar_4

Investment Securities (Summary Of Continuous Unrealized Loss Positions Of Available-For-Sale Security) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Document Period End Date	Sep. 30, 2018
Accumulated Other Comprehensive Income (Loss) [Member]
Unrealized Loss Position For - Estimated Fair Value - Less than 12 Months	$ 7,641	$ 3,582
Unrealized Loss Position For - Unrealized Loss - Less than 12 Months	(219)	(15)
Unrealized Loss Position For - Estimated Fair Value - 12 Months or More	16,855	20,577
Unrealized Loss Position For - Unrealized Loss - 12 Months or More	(1,090)	(451)
Unrealized Loss Position For - Estimated Fair Value - Total	24,496	24,159
Unrealized Loss Position For - Unrealized Loss - Total	$ (1,309)	$ (466)

Investment Securities (Summar_5

Investment Securities (Summary Of Net Gain From Sale Of Agency Securities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cost of Sale of Fair Value Option Securities	$ (1,039)	$ (6,016)	$ (4,017)	$ (8,636)
Cost of Sale of Investment Securities	(3,004)	(6,019)	(7,818)	(14,374)
Proceeds from agency MBS sold			12,381	11,682
Net gain (loss) on sale of investment securities	(40)	22	(116)	(47)
Available-for-sale Securities [Member]
Agency MBS sold, at cost	(1,965)	(3)	(3,801)	(5,738)
Proceeds from agency MBS sold	1,929	2	3,746	5,649
Net gain (loss) on sale of investment securities		(1)		(89)
Gross gain on sale of investment securities	1	0	6	6
Gross loss on sale of investment securities	(37)	(1)	(61)	(95)
Securities Remeasured at Fair Value [Member]
Proceeds from agency MBS sold	1,035	6,039	3,956	8,678
Net gain (loss) on sale of investment securities		23		42
Gross gain on sale of investment securities	2	28	12	48
Gross loss on sale of investment securities	(6)	(5)	(73)	(6)
Securities (Assets) [Member]
Proceeds from agency MBS sold	2,964	6,041	7,702	14,327
Net gain (loss) on sale of investment securities	(40)	22	(116)	(47)
Gross gain on sale of investment securities	3	28	18	54
Gross loss on sale of investment securities	(43)	$ (6)	(134)	$ (101)
Cost and Proceeds of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	(36)		(55)
Cost and Proceeds of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	(4)		(61)
Gross Gain & Loss of Investment Securities [Member] | Available-for-sale Securities [Member]
Net gain (loss) on sale of investment securities	(36)		(55)
Gross Gain & Loss of Investment Securities [Member] | Securities Remeasured at Fair Value [Member]
Net gain (loss) on sale of investment securities	$ (4)		$ (61)

Investment Securities Securitie

Investment Securities Securities by Credit Rating (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Securities, Available-for-sale [Line Items]
Document Period End Date	Sep. 30, 2018
Debt Securities, Trading	$ 47,655	$ 23,427
Debt Securities, Trading and Available-for-sale	72,365	57,080
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	367	0
Debt Securities, Trading and Available-for-sale	374	7
Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	133	29
Debt Securities, Trading and Available-for-sale	133	29
Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	997	876
Debt Securities, Trading and Available-for-sale	997	876
Securities Remeasured at Fair Value [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading and Available-for-sale	997	876
BBB Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	37	0
BBB Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	30	29
BBB Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	67	34
BB Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	8	0
BB Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	5	0
BB Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	428	370
AAA Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	276	7
AAA Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	37	0
AAA Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	0	0
AA Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	21	0
AA Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	61	0
AA Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	0	0
A Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	27	0
A Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	0	0
A Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	17	1
B Rating [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	2	0
B Rating [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	0	0
B Rating [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	458	455
Not Rated [Member] | Mortgage-backed Securities, Issued by Private Enterprises [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	3	0
Not Rated [Member] | Commercial Mortgage Backed Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	0	0
Not Rated [Member] | Credit Risk Transfer Securities [Member]
Debt Securities, Available-for-sale [Line Items]
Debt Securities, Trading	$ 27	$ 16

Repurchase Agreements And Oth_3

Repurchase Agreements And Other Debt (Narrative) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Assets Sold under Agreements to Repurchase [Line Items]
Document Period End Date	Sep. 30, 2018
Securities Sold under Agreements to Repurchase	$ 65,734	$ 50,296
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	15,549	10,467
Debt of consolidated variable interest entities, at fair value	(291)	(357)
TBA securities Fifteen Year and Thirty Year Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Fair Value, Net	(43)	3
TBA and Forward Settling Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Derivative, Forward Settlement Value	9,436	15,739
Derivative, Fair Value, Net	(43)	$ 3
Agency Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Securities Sold under Agreements to Repurchase	$ 65,684
Bethesda Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Percentage of Repurchase Agreement Funding	39.00%	33.00%
FICC [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Percentage of Repurchase Agreement Funding	36.00%	30.00%
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 3,938	$ 2,698

Repurchase Agreements And Oth_4

Repurchase Agreements And Other Debt (Repurchase Arrangements And Weighted Average Interest Rates Classified By Original Maturities) (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)days	Dec. 31, 2017USD ($)days
Document Period End Date	Sep. 30, 2018
Repurchase Agreements	$ 65,734	$ 50,296
Weighted Average Interest Rate	2.30%	1.57%
Weighted Average Days to Maturity | days	67	116
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 15,549	$ 10,467
Maturity Overnight [Member]
Repurchase Agreements	13,961	5,250
30 Days or Less [Member]
Repurchase Agreements	$ 35,815	$ 19,771
Weighted Average Interest Rate	2.29%	1.59%
Weighted Average Days to Maturity | days	9	11
1 to 3 Months
Repurchase Agreements	$ 16,273	$ 16,150
Weighted Average Interest Rate	2.30%	1.50%
Weighted Average Days to Maturity | days	56	50
3 to 6 Months
Repurchase Agreements	$ 9,472	$ 7,287
Weighted Average Interest Rate	2.15%	1.50%
Weighted Average Days to Maturity | days	110	130
6 to 9 Months
Repurchase Agreements	$ 400	$ 2,361
Weighted Average Interest Rate	2.78%	1.66%
Weighted Average Days to Maturity | days	254	225
9 to 12 Months
Repurchase Agreements	$ 700	$ 202
Weighted Average Interest Rate	2.53%	1.64%
Weighted Average Days to Maturity | days	279	297
12 to 24 Months
Repurchase Agreements	$ 2,099	$ 1,700
Weighted Average Interest Rate	2.78%	1.84%
Weighted Average Days to Maturity | days	486	468
24 to 36 Months
Repurchase Agreements	$ 925	$ 2,200
Weighted Average Interest Rate	2.79%	1.80%
Weighted Average Days to Maturity | days	829	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
US Treasury Securities [Member] | 2 Days to 1 Month [Member]
Repurchase Agreements	$ 50	$ 0
Weighted Average Interest Rate	2.32%	0.00%
Weighted Average Days to Maturity | days	1	0
Agency Securities [Member]
Repurchase Agreements	$ 65,684
Weighted Average Days to Maturity | days	67	116
Agency Securities [Member] | Repurchase Agreements [Member]
Weighted Average Interest Rate	2.30%	1.57%
FICC [Member]
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 3,938	$ 2,698

Derivative and Other Hedging _3

Derivative and Other Hedging Instruments (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)month	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)month	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)
Interest Rate Swaption [Member]
Average Maturity (Years)			7 years 9 months 18 days		8 years 10 months 24 days
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month			6		10
Notional Amount	$ 5,600		$ 5,600		$ 6,650
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	30	$ (22)	155	$ (46)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	0	0	1,100	3,750
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	$ 0	0	$ (2,150)	0
Derivative, Average Fixed Interest Rate	2.83%		2.83%		2.72%
Interest Rate Derivatives, at Fair Value, Net	$ 157		$ 157		$ 75
Options At Cost			122		159
TBA and Forward Settling Agency Securities [Member]
Notional Amount	9,274	18,878	9,274	18,878	15,474	$ 19,805	$ 16,867	$ 10,916
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(56)	158	(362)	360
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	55,702	92,803	163,777	185,205
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(90,792)		(177,243)
US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	21	(1)	104	(29)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	427	131	1,455	(78)
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Notional Amount	5,600		5,600
Short [Member] | US Treasury Securities [Member]
Notional Amount	16,213	9,254	16,213	9,254	10,699	13,394	7,358	8,061
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	150	(19)	397	(207)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	(4,402)	5,105	(10,693)	11,595
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	1,583	(3,209)	5,179	(10,402)
Long [Member] | US Treasury Securities [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	1
Trading Securities Added During the Period	792	1	1,841	304
Notional Amount Of Trading Securities Settlement Expiration During The Period	(682)	(1)	(1,731)	(493)
Debt Securities, Trading, and Equity Securities, FV-NI		$ 0		$ 0	$ 0	$ 0	$ 0	$ 189
Long [Member]
Debt Securities, Trading, and Equity Securities, FV-NI	$ 110		$ 110

Derivative and Other Hedging _4

Derivative and Other Hedging Instruments (Fair Value Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Derivative [Line Items]
Derivative asset, fair value	$ 412		$ 412			$ 205
Derivative liability, fair value	(62)		(62)			(28)
Derivative assets, at fair value	412		412			205
Derivative Liability	(62)		(62)			(28)
U.S. Treasury securities	109		109			0
U.S. Treasury Securities - short	(15,549)		(15,549)			(10,467)
Total - (short)/long, net	(15,440)		(15,440)			(10,467)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	427	$ 131	1,455	$ (78)
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	9,274	18,878	9,274	18,878	$ 19,805	15,474	$ 16,867	$ 10,916
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	55,702	92,803	163,777	185,205
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period		(90,792)		(177,243)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	(56)	158	(362)	360
Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	48,675		48,675			43,700
Derivative liability, fair value	(1)		(1)			(1)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	2,150	3,550	9,800	10,575
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(1,350)	(1,400)	(4,825)	(5,600)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	282	15	1,161	(157)
Interest Rate Swap [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	217		217			81
Interest Rate Swaption [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	5,600		5,600			6,650
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	0	0	1,100	3,750
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	0	0	(2,150)	0
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	30	(22)	155	(46)
Interest Rate Swaption [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative [Line Items]
Derivative asset, fair value	157		157			75
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative liability, fair value	(61)		(61)			(27)
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	(66,233)		(169,977)
US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	21	(1)	104	(29)
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member] | Future [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative [Line Items]
Derivative assets, at fair value	20		20			19
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	18		18			30
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	48,675		48,675
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	5,600		5,600
Short [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative Liability, Notional Amount	16,213	9,254	16,213	9,254	13,394	10,699	7,358	8,061
Notional Amount Of Derivatives Not Designated As Hedging Instruments Additions During The Period	(4,402)	5,105	(10,693)	11,595
Notional Amount Of Derivatives Not Designated As Hedging Instruments Settlement Expiration During The Period	1,583	(3,209)	5,179	(10,402)
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	150	(19)	397	(207)
Long [Member]
Derivative [Line Items]
Debt Securities, Trading, and Equity Securities, FV-NI	110		110
Long [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	0	0	0	1
Debt Securities, Trading, and Equity Securities, FV-NI		0		0	$ 0	$ 0	$ 0	$ 189
Trading Securities Added During the Period	792	1	1,841	304
Notional Amount Of Trading Securities Settlement Expiration During The Period	$ (682)	$ (1)	$ (1,731)	$ (493)

Derivative and Other Hedging _5

Derivative and Other Hedging Instruments (Summary Of Outstanding Interest Rate Swaps) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)month	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)month
Document Period End Date			Sep. 30, 2018
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 427	$ 131	$ 1,455	$ (78)
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	30	(22)	$ 155	(46)
Notional Amount	$ 5,600		$ 5,600		$ 6,650
Average Fixed Pay Rate	2.83%		2.83%		2.72%
Options At Cost			$ 122		$ 159
Interest Rate Derivatives, at Fair Value, Net	$ 157		$ 157		$ 75
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month			6		10
Average Maturity (Years)			7 years 9 months 18 days		8 years 10 months 24 days
Forward Contracts [Member] | Interest Rate Swap [Member]
Derivative, Notional Amount	4,900		$ 4,900		$ 4,600
Weighted Average Forward Start Date			6 months		3 months 18 days
Interest Rate Swap [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	282	$ 15	$ 1,161	$ (157)
Notional Amount	$ 48,675		$ 48,675		$ 43,700
Average Fixed Pay Rate	2.01%		2.01%		1.74%
Average Receive Rate	2.33%		2.33%		1.44%
Average Maturity (Years)			4 years 8 months 12 days		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	$ 4,950		$ 4,950		$ 5,100
Average Fixed Pay Rate	2.83%		2.83%		2.71%
Options At Cost			$ 99		$ 118
Interest Rate Derivatives, at Fair Value, Net	$ 127		$ 127		$ 46
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month			4		7
Average Maturity (Years)			7 years 6 months		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	$ 650		$ 650		$ 1,050
Average Fixed Pay Rate	2.80%		2.80%		2.71%
Options At Cost			$ 23		$ 23
Interest Rate Derivatives, at Fair Value, Net	$ 30		$ 30		$ 16
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month			20		18
Average Maturity (Years)			10 years		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
Greater Than Two Years and Less Than or Equal to Three Years [Member] | Interest Rate Swaption [Member]
Notional Amount					$ 500
Average Fixed Pay Rate					2.78%
Options At Cost					$ 18
Interest Rate Derivatives, at Fair Value, Net					$ 13
Cash Flow Hedges Derivative Instruments Not Designated As Hedging Instruments Average Months To Expiration | month					30
Average Maturity (Years)					10 years
Greater Than One Year and Less Than or Equal to Three Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 19,250		$ 19,250		$ 21,025
Average Fixed Pay Rate	1.59%		1.59%		1.40%
Average Receive Rate	2.33%		2.33%		1.46%
Average Maturity (Years)			1 year 2 months 12 days		1 year 6 months
Greater Than Three Years and Less Than or Equal to Five Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 9,975		$ 9,975		$ 6,825
Average Fixed Pay Rate	1.96%		1.96%		1.82%
Average Receive Rate	2.33%		2.33%		1.43%
Average Maturity (Years)			3 years 10 months 24 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	$ 5,025		$ 5,025		$ 5,775
Average Fixed Pay Rate	2.54%		2.54%		2.02%
Average Receive Rate	2.34%		2.34%		1.44%
Average Maturity (Years)			6 years 1 month 6 days		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	$ 10,000		$ 10,000		$ 6,650
Average Fixed Pay Rate	2.33%		2.33%		2.10%
Average Receive Rate	2.33%		2.33%		1.42%
Average Maturity (Years)			8 years 6 months		9 years 1 month 6 days
Greater Than Ten Years [Member] | Interest Rate Swap [Member]
Notional Amount	$ 4,425		$ 4,425		$ 3,425
Average Fixed Pay Rate	2.59%		2.59%		2.49%
Average Receive Rate	2.34%		2.34%		1.45%
Average Maturity (Years)			11 years 9 months 18 days		12 years 10 months 24 days

Derivative and Other Hedging _6

Derivative and Other Hedging Instruments (Remaining Interest Rate Swap Term) (Details) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2018USD ($)month	Sep. 30, 2017USD ($)	Dec. 31, 2017USD ($)month
Document Period End Date			Sep. 30, 2018
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 427	$ 131	$ 1,455	$ (78)
Interest Rate Swaption [Member]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	30	(22)	155	(46)
Cost			122		$ 159
Fair Value	157		$ 157		$ 75
Average Months to Expiration | month			6		10
Derivative Liability, Notional Amount	$ 5,600		$ 5,600		$ 6,650
Average Fixed Pay Rate	2.83%		2.83%		2.72%
Average Maturity (Years)			7 years 9 months 18 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	$ 282	$ 15	$ 1,161	$ (157)
Derivative Liability, Notional Amount	$ 48,675		$ 48,675		$ 43,700
Average Fixed Pay Rate	2.01%		2.01%		1.74%
Average Maturity (Years)			4 years 8 months 12 days		4 years 6 months
Less Than or Equal to One Year [Member] | Interest Rate Swaption [Member]
Cost			$ 99		$ 118
Fair Value	$ 127		$ 127		$ 46
Average Months to Expiration | month			4		7
Derivative Liability, Notional Amount	$ 4,950		$ 4,950		$ 5,100
Average Fixed Pay Rate	2.83%		2.83%		2.71%
Average Maturity (Years)			7 years 6 months		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	$ 19,250		$ 19,250		$ 21,025
Average Fixed Pay Rate	1.59%		1.59%		1.40%
Average Maturity (Years)			1 year 2 months 12 days		1 year 6 months
Bermudan [Member] | Interest Rate Swaption [Member]
Derivative Liability, Notional Amount	$ 700		$ 700
Interest Rate Swaps Excluding Forward Starting [Member] | Interest Rate Swap [Member]
Average Fixed Pay Rate	1.89%		1.89%		1.68%

Derivative and Other Hedging _7

Derivative and Other Hedging Instruments (US Treasury Securities) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Document Period End Date	Sep. 30, 2018
U.S. Treasury securities, net	$ (15,440)	$ (10,467)
Weighted Average Yield Percentage	3.22%	2.89%
7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	$ (10,319)	$ (6,131)
At Par Value [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(16,103)	(10,699)
US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	20	19
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(9,274)	(15,474)
Derivative, Forward Settlement Value	(9,436)	(15,739)
Derivative Asset, Fair Value, Gross Asset	(9,393)	(15,742)
Derivative, Fair Value, Net	(43)	3
5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(230)	(288)
10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(5,554)	(4,280)
10 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	20	15
5 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Fair Value, Net	0	4
Short [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(1,650)	(2,910)
Derivative, Forward Settlement Value	(1,980)	(3,570)
Derivative Asset, Fair Value, Gross Asset	(1,960)	(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	(1,980)	(2,718)
Derivative Asset, Fair Value, Gross Asset	(1,960)	(2,703)
Short [Member] | 5 Year Maturity [Member] | US Treasury Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	0	(730)
Derivative, Forward Settlement Value	0	(852)
Derivative Asset, Fair Value, Gross Asset	0	(848)
Fair Value Hedging [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(15,440)	(10,467)
Fair Value Hedging [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(9,989)	(6,029)
Fair Value Hedging [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(228)	(283)
Fair Value Hedging [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(5,223)	(4,155)
At Cost Basis [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(15,995)	(10,622)
At Cost Basis [Member] | 7 Years Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(10,274)	(6,106)
At Cost Basis [Member] | 5 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	(229)	(286)
At Cost Basis [Member] | 10 Year Maturity [Member]
Derivative [Line Items]
U.S. Treasury securities, net	$ (5,492)	$ (4,230)
US Treasury Securities [Member]
Derivative [Line Items]
Weighted Average Yield Percentage	2.43%	2.12%

Derivative and Other Hedging _8

Derivative and Other Hedging Instruments (TBA Securities by Coupon and Issuer) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Document Period End Date	Sep. 30, 2018
TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	$ (9,274)	$ (15,474)
Cost Basis	(9,436)	(15,739)
Net long TBA position, at fair value	(9,393)	(15,742)
TBA, net carrying value	(43)	3
30 Year Maturity [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(4,643)	(10,526)
Cost Basis	(4,762)	(10,714)
Net long TBA position, at fair value	(4,739)	(10,727)
TBA, net carrying value	(23)	13
30 Year Maturity [Member] | 3.0% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(843)	(4,317)
Cost Basis	(812)	(4,303)
Net long TBA position, at fair value	(805)	(4,312)
TBA, net carrying value	(7)	9
30 Year Maturity [Member] | 3.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount		(3,932)
Cost Basis		(4,027)
Net long TBA position, at fair value		(4,034)
TBA, net carrying value	12	7
30 Year Maturity [Member] | 4.0% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(3,024)	(2,338)
Cost Basis	(3,071)	(2,449)
Net long TBA position, at fair value	(3,052)	(2,446)
TBA, net carrying value	(19)	(3)
30 Year Maturity [Member] | 4.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(2,475)
Cost Basis	(2,562)
Net long TBA position, at fair value	(2,553)
TBA, net carrying value	(9)	0
30 Year Maturity [Member] | Short [Member] | 3.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(1,699)
Cost Basis	(1,683)
Net long TBA position, at fair value	(1,671)
30 Year Maturity [Member] | Short [Member] | 4.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount		(61)
Cost Basis		(65)
Net long TBA position, at fair value		(65)
15 Year Maturity [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(4,631)	(4,948)
Cost Basis	(4,674)	(5,025)
Net long TBA position, at fair value	(4,654)	(5,015)
TBA, net carrying value	(20)	(10)
15 Year Maturity [Member] | 2.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(194)	(1,373)
Cost Basis	(190)	(1,372)
Net long TBA position, at fair value	(188)	(1,370)
TBA, net carrying value	(2)	(2)
15 Year Maturity [Member] | 3.0% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(567)	(3,161)
Cost Basis	(565)	(3,225)
Net long TBA position, at fair value	(560)	(3,217)
TBA, net carrying value	(5)	(8)
15 Year Maturity [Member] | 3.5% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(2,646)	(414)
Cost Basis	(2,669)	(428)
Net long TBA position, at fair value	(2,658)	(428)
TBA, net carrying value	(11)	0
15 Year Maturity [Member] | 4.0% Coupon [Member] | TBA and Forward Settling Agency Securities [Member]
Derivative [Line Items]
Derivative, Notional Amount	(1,224)	0
Cost Basis	(1,250)	0
Net long TBA position, at fair value	(1,248)	0
TBA, net carrying value	$ (2)	$ 0

Derivative and Other Hedging _9

Derivative and Other Hedging Instruments (Effect Of Derivative Instruments Not Designated As Hedges On Comprehensive Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	$ 427	$ 131	$ 1,455	$ (78)
Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			(6,650)
Additions	0	0	(1,100)	(3,750)
Settlement, Expirations or Exercise	0	0	2,150	0
Notional Amount	(5,600)		(5,600)
Amount Gain/(Loss) Recognized in Income on Derivatives	30	(22)	155	(46)
TBA and Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(19,805)	(16,867)	(15,474)	(10,916)
Additions	(55,702)	(92,803)	(163,777)	(185,205)
Settlement, Expirations or Exercise		90,792		177,243
Notional Amount	(9,274)	(18,878)	(9,274)	(18,878)
Amount Gain/(Loss) Recognized in Income on Derivatives	(56)	158	(362)	360
Derivative, Notional Amount	(9,274)		(9,274)			$ (15,474)
Purchases Of TBAs And Forward Settling Agency Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Settlement, Expirations or Exercise	66,233		169,977
Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount			(43,700)
Additions	(2,150)	(3,550)	(9,800)	(10,575)
Settlement, Expirations or Exercise	1,350	1,400	4,825	5,600
Notional Amount	(48,675)		(48,675)
Amount Gain/(Loss) Recognized in Income on Derivatives	282	15	1,161	(157)
US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	21	(1)	104	(29)
Not Designated as Hedging Instrument [Member] | Interest Rate Swaption [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(5,600)		(5,600)
Derivative, Notional Amount		(4,950)		(4,950)	$ (5,600)	(6,650)	$ (4,950)	$ (1,200)
Not Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(48,675)		(48,675)
Derivative, Notional Amount		(42,150)		(42,150)	(47,875)	(43,700)	(40,000)	(37,175)
Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(13,394)	(7,358)	(10,699)	(8,061)
Additions	4,402	(5,105)	10,693	(11,595)
Settlement, Expirations or Exercise	(1,583)	3,209	(5,179)	10,402
Notional Amount	(16,213)	(9,254)	(16,213)	(9,254)
Amount Gain/(Loss) Recognized in Income on Derivatives	150	(19)	397	(207)
Derivative, Notional Amount	(1,650)		(1,650)			(2,910)
Long [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Debt Securities, Trading, and Equity Securities, FV-NI	110		110
Long [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Amount Gain/(Loss) Recognized in Income on Derivatives	0	0	0	1
Debt Securities, Trading, and Equity Securities, FV-NI		0		0	$ 0	$ 0	$ 0	$ 189
Trading Securities Added During the Period	792	1	1,841	304
Notional Amount Of Trading Securities Settlement Expiration During The Period	(682)	(1)	(1,731)	(493)
Future [Member] | Short [Member] | US Treasury Securities [Member]
Changes in Derivative and Other Hedge Portfolio [Roll Forward]
Notional Amount	(1,650)	(2,910)	(2,910)	(1,810)
Additions	1,650	(2,910)	6,209	(8,430)
Settlement, Expirations or Exercise	(1,650)	2,910	(7,469)	7,330
Notional Amount	$ (1,650)	$ (2,910)	$ (1,650)	$ (2,910)

Pledged Assets (Narrative) (Det

Pledged Assets (Narrative) (Details)	Sep. 30, 2018
Pledged Assets [Abstract]
Risk Of Repurchase Agreement To Stockholders Equity	4.00%

Pledged Assets Repurchase Agree

Pledged Assets Repurchase Agreements with Counterparties Greater than or Equal to 5% of Equity at Risk (Details) $ in Millions	9 Months Ended
	Sep. 30, 2018USD ($)days	Dec. 31, 2017USD ($)days
Repurchase Agreements with Counterparties Greater than or equal to 5% of Equity at Risk [Line Items]
Document Period End Date	Sep. 30, 2018
Securities Sold under Agreements to Repurchase | $	$ 65,734	$ 50,296
Risk Of Repurchase Agreement To Stockholders Equity	4.00%
Weighted Average Days to Maturity | days	67	116
FICC [Member]
Repurchase Agreements with Counterparties Greater than or equal to 5% of Equity at Risk [Line Items]
Risk Of Repurchase Agreement To Stockholders Equity	7.50%

Pledged Assets (Assets Pledged

Pledged Assets (Assets Pledged as Collateral) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	$ 68,109	$ 52,497
Document Period End Date	Sep. 30, 2018
Retained Interests in Consolidated VIE's Pledged as Collateral Under Repurchase Agreements	$ 163	182
Accrued interest on pledged securities	215	158
Restricted cash and cash equivalents	456	317
Total Fair Value of Securities Pledged and Accrued Interest	70,191
Total Fair Value Of Agency Securities Pledged And Accrued Interest		54,559
Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	68,065	52,497
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	184	221
Accrued interest on pledged securities		1
Restricted cash and cash equivalents	378	281
Total Fair Value of Securities Pledged and Accrued Interest	621
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	212	153
Total Fair Value of Securities Pledged and Accrued Interest	68,869
Total Fair Value Of Agency Securities Pledged And Accrued Interest		52,798
Variable Interest Entity, Primary Beneficiary [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	453	662
Accrued interest on pledged securities	1	2
Total Fair Value of Securities Pledged and Accrued Interest	454
Total Fair Value Of Agency Securities Pledged And Accrued Interest		664
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	246	519
Accrued interest on pledged securities	1	2
Total Fair Value of Securities Pledged and Accrued Interest	247
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]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	68,948	53,899
Credit Risk Transfer Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	44	0
Credit Risk Transfer Securities [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	44
Credit Risk Transfer Securities [Member] | Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	0
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	528	185
US Treasury Securities [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	470	113
US Treasury Securities [Member] | Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	58	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	78	35
Under Prime Broker Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash and cash equivalents	0	1
Excluding Cash Received [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted cash and cash equivalents	$ 456	$ 317

Pledged Assets (Securities Pled

Pledged Assets (Securities Pledged as Collateral) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Document Period End Date	Sep. 30, 2018
Retained Interests in Consolidated VIE's Pledged as Collateral Under Repo	$ 163	$ 182
Security Owned and Pledged as Collateral, Fair Value	68,109	52,497
Agency Securities Pledged As Collateral Amortized Cost	70,379	52,899
Agency Securities Pledged As Collateral Accrued Interest	212	153
Maturity Less than 30 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	36,636	20,162
Agency Securities Pledged As Collateral Amortized Cost	37,892	20,313
Agency Securities Pledged As Collateral Accrued Interest	114	59
Maturity 31 To 59 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	9,512	12,950
Agency Securities Pledged As Collateral Amortized Cost	9,728	13,061
Agency Securities Pledged As Collateral Accrued Interest	29	38
Maturity 60 To 90 Days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	7,774	4,000
Agency Securities Pledged As Collateral Amortized Cost	8,017	4,013
Agency Securities Pledged As Collateral Accrued Interest	25	11
Maturity over 90 days [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	14,187	15,385
Agency Securities Pledged As Collateral Amortized Cost	14,742	15,512
Agency Securities Pledged As Collateral Accrued Interest	44	45
US Treasury Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Security Owned and Pledged as Collateral, Fair Value	528	$ 185
Securities Received as Collateral, Amount Repledged and Sold	$ 426

Pledged Assets (Assets Pledge_2

Pledged Assets (Assets Pledged from Counterparties) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Document Period End Date	Sep. 30, 2018
Obligation to Return Securities Borrowed Under Reverse Repurchase Agreements at Fair Value	$ 15,549	$ 10,467
Restricted Cash and Cash Equivalents	456	317
Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	282	82
Restricted Cash and Securities Pledged	16,527	10,935
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Securities Pledged	362	82
US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	16,245	10,853
Reverse Repurchase Agreements [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	16,165	10,853
Reverse Repurchase Agreements [Member] | US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	16,165	10,853
Derivative [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	378	281
Derivative [Member] | US Treasury Securities [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Pledged Financial Instruments, Not Separately Reported, Mortgage-Related Securities Available-for-sale or Held-for-investment	80	0
Derivative [Member] | Assets Pledged to Us [Member]
Offsetting Assets and Liabilities [Line Items]
Restricted Cash and Cash Equivalents	$ 282	$ 82

Pledged Assets (Offsetting Asse

Pledged Assets (Offsetting Assets and Liabilities) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Offsetting Assets and Liabilities [Line Items]
Document Period End Date	Sep. 30, 2018
Collateral Received	$ (3,370)
Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	16,701	$ 11,147
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	16,701	11,147
Financial Instruments	(13,288)	(9,705)
Collateral Received		(1,361)
Net Amount	43	81
Assets [Member] | ERROR in label resolution.
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	374	156
Net Amounts of Assets Presented in the Consolidated Balance Sheets	374	156
Financial Instruments	(1)	(1)
Collateral Received	(334)	(82)
Net Amount	39	73
Assets [Member] | TBA and Forward Settling Agency Securities [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	18	30
Net Amounts of Assets Presented in the Consolidated Balance Sheets	18	30
Financial Instruments	(18)	(22)
Net Amount	0	8
Assets [Member] | Reverse Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Net Amount	4
Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	65,796	50,324
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	65,796	50,324
Financial Instruments	(13,288)	(9,705)
Collateral Received	(52,508)	(40,619)
Net Amount	0
Liability [Member] | Repurchase Agreements [Member]
Offsetting Assets and Liabilities [Line Items]
Net Amount	0	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	61	27
Net Amounts of Assets Presented in the Consolidated Balance Sheets	61	27
Financial Instruments	(18)	(22)
Collateral Received	(43)	(5)
Net Amount	0	0
Reverse Repurchase Agreements [Member] | Assets [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	16,309	10,961
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	16,309	10,961
Financial Instruments	(13,269)	(9,682)
Collateral Received	(3,036)	(1,279)
Repurchase Agreements [Member] | Liability [Member]
Offsetting Assets and Liabilities [Line Items]
Gross Amounts of Recognized Assets	65,734	50,296
Gross Amount Offset in the Consolidated Balance Sheets	0
Net Amounts of Assets Presented in the Consolidated Balance Sheets	65,734	50,296
Financial Instruments	(13,269)	(9,682)
Collateral Received	$ (52,465)	$ (40,614)

Fair Value Measurements (Detail

Fair Value Measurements (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 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	$ 20	$ 19
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	157	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	217	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	$ 18	30
Transfers between hierarchy levels	0
Agency securities	$ 70,408	55,506
Agency securities transferred to consolidated VIEs	453	662
Non-Agency Securities, at Fair Value	507	36
Financial Instruments, Owned, Other, at Fair Value	997	876
U.S. Treasury securities	109	0
Equity Securities, FV-NI	0	29
TBA securities	412	205
Derivative Liability	62	28
Debt of consolidated variable interest entities, at fair value	291	357
Obligation to return securities borrowed under reverse repurchase agreements, at fair value	15,549	10,467
Interest rate swaps	412	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	129	48
Total liabilities	15,549	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	72,757	57,266
Total liabilities	353	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	$ 61	$ 27

Net Income (Loss) Per Common _2

Net Income (Loss) Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted Average Number of Shares Outstanding, Basic	462.3	364.7	419.8	347.5
Dilutive Securities, Effect on Basic Earnings Per Share, Options and Restrictive Stock Units	$ 0.4	$ 0.2	$ 0.3	$ 0.1
Weighted Average Number of Shares Outstanding, Diluted	462.7	364.9	420.1	347.6
Net Income (Loss) Available to Common Stockholders, Basic	$ 207	$ 271	$ 906	$ 357
Earnings Per Share, Basic	$ 0.45	$ 0.74	$ 2.16	$ 1.03
Earnings Per Share, Diluted	$ 0.45	$ 0.74	$ 2.16	$ 1.03

Stockholders' Equity (Preferred

Stockholders' Equity (Preferred Stock) (Details) - $ / shares	1 Months Ended	9 Months Ended	12 Months Ended
	May 31, 2014	Sep. 30, 2018	Dec. 31, 2017	Sep. 12, 2017	May 05, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Document Period End Date		Sep. 30, 2018
Preferred Stock Authorized, but not Issued		10,000,000
Preferred Stock, Shares Authorized		10,000,000
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
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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	$ (193)	$ 90	$ (959)	$ 257
Agency Securities [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning OCI Balance	(1,111)	(230)	(345)	(397)
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax	(229)	89	(1,014)	168
Amounts reclassified from accumulated OCI	36	1	55	89
Ending OCI Balance	$ (1,304)	$ (140)	$ (1,304)	$ (140)

Stockholders' Equity (Follow-On

Stockholders' Equity (Follow-On Equity Offerings) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Aug. 03, 2018	Jun. 30, 2018	May 29, 2018	Sep. 30, 2017	Sep. 12, 2017	May 05, 2017	Sep. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Document Period End Date							Sep. 30, 2018
Stock Issued During Period, Shares, New Issues	43.7	8.3	34.5	7.6	28.2	24.5
Stock Issued During Period, Value, New Issues	$ 1,000	$ 0	$ 1,000	$ 0	$ 1,000	$ 1,000	$ 1,605	$ 1,238
Sale of Stock, Price Per Share	$ 18.68		$ 18.35	$ 20.96	$ 20.47	$ 20.51	$ 18.73	$ 20.96
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock Issued During Period, Shares, New Issues							86.5	60.3
Stock Issued During Period, Value, New Issues							$ 1	$ 1

Stockholders' Equity (At-the-Ma

Stockholders' Equity (At-the-Market Offering Program) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	Aug. 03, 2018	Jun. 30, 2018	May 29, 2018	Sep. 30, 2017	Sep. 12, 2017	May 05, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 14, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, Value of Shares Approved for Future Issuance									$ 1,000
Common Stock, Shares Authorized							$ 881
Stock Issued During Period, Shares, New Issues	43.7	8.3	34.5	7.6	28.2	24.5
Stock Issued During Period, Value, New Issues	$ 1,000	$ 0	$ 1,000	$ 0	$ 1,000	$ 1,000	$ 1,605	$ 1,238
Sale of Stock, Price Per Share	$ 18.68		$ 18.35	$ 20.96	$ 20.47	$ 20.51	$ 18.73	$ 20.96

Subsequent Event (Details)

Subsequent Event (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	Oct. 11, 2018	Aug. 03, 2018	Jun. 30, 2018	May 29, 2018	May 02, 2018	Sep. 30, 2017	Sep. 12, 2017	May 05, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared									$ 0.54	$ 0.54	$ 1.62	$ 1.62
Stock Issued During Period, Shares, New Issues		43.7	8.3	34.5		7.6	28.2	24.5
Stock Issued During Period, Value, New Issues		$ 1,000,000	$ 0	$ 1,000,000		$ 0	$ 1,000,000	$ 1,000,000			$ 1,605,000	$ 1,238,000
Gain (Loss) on Contract Termination					$ 41,700
Sale of Stock, Price Per Share		$ 18.68		$ 18.35		$ 20.96	$ 20.47	$ 20.51	$ 18.73	$ 20.96	$ 18.73	$ 20.96
Subsequent Event [Member]
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.18
Common Stock [Member]
Subsequent Event [Line Items]
Stock Issued During Period, Shares, New Issues											86.5	60.3
Stock Issued During Period, Value, New Issues											$ 1,000	$ 1,000

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