Collateral Positions (Details) (USD $)	Jun. 30, 2014		Dec. 31, 2013
Collateral Positions
Assets Pledged	$ 10,349,034,000		$ 10,227,092,000
Collateral Held	446,375,000		383,743,000
Derivative contracts
Collateral Positions
Assets Pledged	127,691,000		111,379,000
Derivative contracts | Agency MBS
Collateral Positions
Assets Pledged	75,061,000		73,859,000
Derivative contracts | Cash
Collateral Positions
Assets Pledged	52,630,000	[1]	37,520,000	[1]
Repurchase Agreement Borrowings
Collateral Positions
Assets Pledged	10,221,343,000		10,115,713,000
Repurchase Agreement Borrowings | Agency MBS
Collateral Positions
Assets Pledged	6,074,987,000		6,068,447,000
Repurchase Agreement Borrowings | Cash
Collateral Positions
Assets Pledged	1,800,000	[1]	0	[1]
Repurchase Agreement Borrowings | Non-Agency MBS
Collateral Positions
Assets Pledged	3,698,181,000	[2],[3]	3,663,523,000	[2],[3]
Non-Agency MBS acquired from consolidated VIEs	1,955,000,000		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	732,600,000		738,300,000
Repurchase Agreement Borrowings | U.S. Treasury securities
Collateral Positions
Assets Pledged	446,375,000		383,743,000
Reverse Repurchase Agreements:
Collateral Positions
Collateral Held	446,375,000		383,743,000
Reverse Repurchase Agreements: | U.S. Treasury securities
Collateral Positions
Collateral Held	$ 446,375,000		$ 383,743,000

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

[2] In addition, $732.6 million and $738.3 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 June 30, 2014 and December 31, 2013, respectively.

[3] Includes $1.955 billion and $1.885 billion of Non-Agency MBS acquired in connection with resecuritization transactions from consolidated VIEs at June 30, 2014 and December 31, 2013, respectively, that are eliminated from the Company’s consolidated balance sheets.