Collateral Positions (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
Collateral Positions
Assets Pledged	$ 10,227,092,000		$ 10,624,276,000
Collateral Held	383,743,000		408,833,000
Derivative contracts
Collateral Positions
Assets Pledged	111,379,000		73,931,000
Derivative contracts | Agency MBS
Collateral Positions
Assets Pledged	73,859,000		68,915,000
Derivative contracts | Cash
Collateral Positions
Assets Pledged	37,520,000	[1]	5,016,000	[1]
Repurchase agreements
Collateral Positions
Assets Pledged	10,115,713,000		10,550,345,000
Repurchase agreements | Agency MBS
Collateral Positions
Assets Pledged	6,068,447,000		6,678,384,000
Repurchase agreements | Non-Agency MBS
Collateral Positions
Assets Pledged	3,663,523,000	[2],[3]	3,463,128,000	[2],[3]
Non-Agency MBS acquired from consolidated VIEs	1,885,000,000		1,860,000,000
Non-Agency MBS pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty	738,300,000		759,200,000
Repurchase agreements | U.S. Treasury securities
Collateral Positions
Assets Pledged	383,743,000		408,833,000
Reverse Repurchase Agreements:
Collateral Positions
Collateral Held	383,743,000		408,833,000
Reverse Repurchase Agreements: | U.S. Treasury securities
Collateral Positions
Collateral Held	383,743,000		408,833,000
Non-Agency MBS | Repurchase agreements
Collateral Positions
Non-Agency MBS acquired from consolidated VIEs	$ 1,885,000,000		$ 1,860,000,000

[1] Cash pledged as collateral is reported as “restricted cash” on the Company’s consolidated balance sheets.

[2] In addition, $738.3 million and $759.2 million of Non-Agency MBS are pledged as collateral in connection with contemporaneous repurchase and reverse repurchase agreements entered into with a single counterparty at December 31, 2013 and 2012, respectively.

[3] Includes $1.885 billion and $1.860 billion of Non-Agency MBS acquired in connection with resecuritization transactions from consolidated VIEs at December 31, 2013 and 2012, respectively, that are eliminated from the Company’s consolidated balance sheets.