Repurchase Agreements (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 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	$ 3,447,050	$ 3,580,754
Repurchage agreement, Weighted Average Interest Rate	0.54%	0.61%
Fair Value of Collateral Pledged	3,783,581	3,890,066
Deferred Costs	(35)	(243)
Repurchase Agreement Counterparty, Weighted Average Maturity of Agreements	70 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	15,576	20,651
Repurchage agreement, Weighted Average Interest Rate	1.50%	1.59%
Fair Value of Collateral Pledged	17,775	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	2,242,441	2,522,503
Repurchage agreement, Weighted Average Interest Rate	0.33%	0.42%
Fair Value of Collateral Pledged	2,332,716	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	10,279	10,569
Repurchage agreement, Weighted Average Interest Rate	1.65%	1.80%
Fair Value of Collateral Pledged	12,735	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	262,822	246,849
Repurchage agreement, Weighted Average Interest Rate	0.35%	0.39%
Fair Value of Collateral Pledged	316,139	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	321,769	303,674
Repurchage agreement, Weighted Average Interest Rate	1.18%	1.27%
Fair Value of Collateral Pledged	391,437	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	377,554	369,948
Repurchage agreement, Weighted Average Interest Rate	0.97%	1.16%
Fair Value of Collateral Pledged	447,501	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	216,644	106,803
Repurchage agreement, Weighted Average Interest Rate	1.10%	1.27%
Fair Value of Collateral Pledged	$ 265,278	$ 136,227