Collateral Positions (Details 2) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	$ 10,017,556,000
Agency MBS
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	5,533,210,000
Non-Agency MBS
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	3,664,579,000
U.S. Treasury securities
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	512,105,000
CRT securities
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	94,676,000
Residential whole loans
Collateral Positions
Total Fair Value of Assets Pledged and Accrued Interest	212,986,000
Derivative Hedging Instruments
Collateral Positions
Fair Value	57,247,000
Amortized Cost	58,235,000
Accrued Interest on Pledged Assets	120,000
Derivative Hedging Instruments \| Agency MBS
Collateral Positions
Fair Value	57,247,000
Amortized Cost	58,235,000
Accrued Interest on Pledged Assets	120,000
Derivative Hedging Instruments \| Non-Agency MBS
Collateral Positions
Fair Value	0
Amortized Cost	0
Accrued Interest on Pledged Assets	0
Derivative Hedging Instruments \| U.S. Treasury securities
Collateral Positions
Fair Value	0
Amortized Cost	0
Accrued Interest on Pledged Assets	0
Derivative Hedging Instruments \| CRT securities
Collateral Positions
Fair Value	0
Amortized Cost	0
Accrued Interest on Pledged Assets	0
Derivative Hedging Instruments \| Residential whole loans
Collateral Positions
Fair Value	0
Amortized Cost	0
Accrued Interest on Pledged Assets	0
Repurchase Agreements
Collateral Positions
Fair Value	9,934,267,000
Amortized Cost	9,042,625,000
Accrued Interest on Pledged Assets	25,922,000
Repurchase Agreements \| Agency MBS
Collateral Positions
Fair Value	5,462,566,000
Amortized Cost	5,390,415,000
Accrued Interest on Pledged Assets	13,277,000
Repurchase Agreements \| Non-Agency MBS
Collateral Positions
Fair Value	3,652,000,000
Amortized Cost	2,832,577,000
Accrued Interest on Pledged Assets	12,579,000
Non-Agency MBS acquired from consolidated VIEs in connection with resecuritization transactions	1,275,000,000	1,885,000,000
Non-Agency MBS pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty	731,000,000	738,300,000
Repurchase Agreements \| U.S. Treasury securities
Collateral Positions
Fair Value	512,105,000
Amortized Cost	512,105,000
Accrued Interest on Pledged Assets	0
Repurchase Agreements \| CRT securities
Collateral Positions
Fair Value	94,610,000
Amortized Cost	96,474,000
Accrued Interest on Pledged Assets	66,000
Repurchase Agreements \| Residential whole loans
Collateral Positions
Fair Value	212,986,000
Amortized Cost	211,054,000
Accrued Interest on Pledged Assets	$ 0

Represents the amount of interest receivable on securities pledged as collateral.

No definition available.

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- Definition

For an unclassified balance sheet, represents investments in debt and equity securities, categorized neither as held-to-maturity nor trading, which are acquired from a consolidated variable interest entity and eliminated on the entity's consolidated balance sheet.

+ References

No definition available.

+ Details

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- Definition

Represents the non-agency MBS pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty.

+ References

No definition available.

+ Details

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- Definition

Sum of the fair values as of the date of the latest financial statement presented of securities pledged as collateral and the amount of interest receivable on the securities pledged as collateral.

+ References

No definition available.

+ Details

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- Definition

Represents the cost of debt and equity securities pledged as collateral, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

No definition available.

+ Details

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- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)(i)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

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