Non Agency MBS (Details) (Non-Agency MBS [Member], USD $)	6 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Principal/par value	$ 492,480,000		$ 376,972,000
Unamortized premium	66,623,000		54,885,000
Unamortized discount	(22,978,000)		(18,514,000)
Amortized cost	536,125,000		413,343,000
Available for sale securities, gross unrealized gains	24,980,000		13,206,000
Available for sale securities, gross unrealized losses	(2,139,000)		(5,453,000)
Total MBS investments at fair value	558,966,000		421,096,000
Weighted average coupon, MBS	5.43%		5.85%
RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Principal/par value	19,282,000		17,119,000
Unamortized premium	4,000		0
Unamortized discount	(855,000)		(1,003,000)
Amortized cost	18,431,000		16,116,000
Available for sale securities, gross unrealized gains	478,000		507,000
Available for sale securities, gross unrealized losses	(801,000)		(1,353,000)
Total MBS investments at fair value			15,270,000
Weighted average coupon, MBS	4.43%		4.41%
CMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Principal/par value	473,198,000		359,853,000
Unamortized premium	3,018,000		3,646,000
Unamortized discount	(22,123,000)		(17,511,000)
Amortized cost	454,093,000		345,988,000
Available for sale securities, gross unrealized gains	22,031,000		11,806,000
Available for sale securities, gross unrealized losses	(1,256,000)		(3,724,000)
Total MBS investments at fair value	474,868,000		354,070,000
Weighted average coupon, MBS	5.47%		5.91%
Payments to Acquire Mortgage Backed Securities (MBS)	120,697,000
CMBS - IO [Member]
Schedule of Available-for-sale Securities [Line Items]
Principal/par value	0	[1]	0	[2]
Unamortized premium	63,601,000	[1]	51,239,000	[2]
Unamortized discount	0	[1]	0	[2]
Amortized cost	63,601,000	[1]	51,239,000	[2]
Available for sale securities, gross unrealized gains	2,471,000	[1]	893,000	[2]
Available for sale securities, gross unrealized losses	(82,000)	[1]	(376,000)	[2]
Total MBS investments at fair value	65,990,000	[1]	51,756,000	[2]
Weighted average coupon, MBS	1.26%	[1]	1.24%	[2]
Payments to Acquire Mortgage Backed Securities (MBS)	16,000
Notional balance of non-Agency IO investments	1,011,637,000		906,202,000
Estimate of Fair Value, Fair Value Disclosure [Member] | RMBS [Member]
Schedule of Available-for-sale Securities [Line Items]
Total MBS investments at fair value	$ 18,108,000

[1] The combined notional balance for the non-Agency CMBS IO securities is $1,011,637 as of June 30, 2012.

[2] The combined notional balance for the non-Agency CMBS IO securities is $906,202 as of December 31, 2011.