Repurchase Agreements (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	$ 3,150,254	$ 3,580,754
Repurchage agreement, Weighted Average Interest Rate	0.53%	0.61%
Fair Value of Collateral Pledged		3,890,066
Deferred Costs	0	(243)
Repurchase Agreement Counterparty, Weighted Average Maturity of Agreements	106 days	114 days
Collateralized Mortgage Obligations [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings		20,651
Repurchage agreement, Weighted Average Interest Rate	1.50%	1.59%
Fair Value of Collateral Pledged		19,686
Residential Mortgage Backed Securities [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	2,081,924	2,522,503
Repurchage agreement, Weighted Average Interest Rate	0.36%	0.42%
Fair Value of Collateral Pledged	2,168,095	2,598,158
Residential Mortgage Backed Securities [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	7,724	10,569
Repurchage agreement, Weighted Average Interest Rate	1.67%	1.80%
Fair Value of Collateral Pledged	8,803	12,746
Commercial Mortgage Backed Securities [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	258,024	246,849
Repurchage agreement, Weighted Average Interest Rate	0.33%	0.39%
Fair Value of Collateral Pledged	302,352	306,318
Commercial Mortgage Backed Securities [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	198,203	303,674
Repurchage agreement, Weighted Average Interest Rate	1.16%	1.27%
Fair Value of Collateral Pledged	240,802	367,859
CMBS IO [Member] | Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	351,518	369,948
Repurchage agreement, Weighted Average Interest Rate	0.94%	1.16%
Fair Value of Collateral Pledged	411,686	449,072
CMBS IO [Member] | Non-Agency MBS [Member]
Assets and Associated Liabilities of Transfers Accounted for as Secured Borrowings [Line Items]
Repurchase Agreements Accounted for as Secured Borrowings	242,458	106,803
Repurchage agreement, Weighted Average Interest Rate	1.03%	1.27%
Fair Value of Collateral Pledged	$ 288,202	$ 136,227