Repurchase Agreements (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014 counterparty		Dec. 31, 2013
Information about MBS
Repurchase agreements	$ 8,606,129	[1]	$ 8,339,297	[1]
Number of counterparties	26
Threshold percent of stockholders' equity at risk with single counterparty to repurchase agreements or Linked Transactions	5.00%
Repurchase Agreement Borrowings
Information about MBS
Repurchase agreements	8,606,129	[2],[3]	8,339,297	[2]
Weighted Average Interest Rate (as a percent)	0.70%		0.77%
Repurchase Agreement Borrowings | Overnight
Information about MBS
Repurchase agreements	0	[3]
Weighted Average Interest Rate (as a percent)	0.00%
Repurchase Agreement Borrowings | Within 30 days
Information about MBS
Repurchase agreements	7,039,400	[3]
Weighted Average Interest Rate (as a percent)	0.54%
Repurchase Agreement Borrowings | Over 30 days to 90 days
Information about MBS
Repurchase agreements	1,036,048	[3]
Weighted Average Interest Rate (as a percent)	1.20%
Repurchase Agreement Borrowings | Over 90 days to 12 months
Information about MBS
Repurchase agreements	216,421	[3]
Weighted Average Interest Rate (as a percent)	1.84%
Repurchase Agreement Borrowings | Over 12 Months
Information about MBS
Repurchase agreements	314,260	[3]
Weighted Average Interest Rate (as a percent)	1.92%
Repurchase Agreement Borrowings | Non-Agency MBS
Information about MBS
Repurchase agreements	2,155,402	[4]	2,206,586	[4]
Linked Transactions | Non-Agency MBS
Information about MBS
Linked repurchase agreements	$ 206,000		$ 102,700

[1] The fair value of securities pledged against the Company’s repurchase agreements was $10.476 billion and $10.116 billion at March 31, 2014 and December 31, 2013, respectively.

[2] At March 31, 2014 and December 31, 2013, the Company had repurchase agreements of $206.0 million and $102.7 million, respectively, that were linked to Non-Agency MBS purchases and accounted for as Linked Transactions, and as such, the linked repurchase agreements are not included in the above table. (See Note 5)

[3] At March 31, 2014, the Company had repurchase agreements of $206.0 million that were linked to Non-Agency MBS purchases and were accounted for as Linked Transactions, and as such, the linked repurchase agreements are not included in the above table. (See Note 5)

[4] Does not reflect Non-Agency MBS and repurchase agreement borrowings that are components of Linked Transactions.