Debt Securities (Details 2) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended
	Jun. 30, 2011 loan	Sep. 30, 2010	Dec. 31, 2011	Dec. 31, 2010
Mortgage-Backed Securities Available-for-Sale
Gain from sale of available-for-sale securities			$ 10,653,000	$ 2,118,000
Unrealized Losses
MBS credit losses			6,001,000
Mortgage-backed securities
Mortgage-Backed Securities Available-for-Sale
Description of variable rate basis			one-month LIBOR	one-month LIBOR
Estimated Fair Value
Securities within a loss less than 12 months			246,889,000
Securities within a loss greater than 12 months			2,684,000
Unrealized Losses
Securities within a loss less than 12 months			(3,011,000)
Securities in a loss greater than 12 months			(399,000)
Number of securities with unrealized loss position			42
Number of securities with recognized other-than-temporary impairment charge			25
Other-than-temporary impairment charge recognized relating to security			4,700,000
Credit losses included in other-than-temporary impairment charges recognized relating to security			3,400,000
MBS credit losses			6,000,000
Number of securities with unrealized losses excluding other than temporarily impaired securities			17
Estimated Fair Value				44,752,000
Unrealized Losses				(1,480,000)
CMBS
Mortgage-Backed Securities Available-for-Sale
Sales/Maturities			238,739,000
Principal payments received			44,449,000
Number of loans reclassified from loans held for investment to mortgage-backed securities, available-for-sale	1
Loan reclassified from loans held for investment to MBS, available-for-sale	176,600,000
Unrealized gain recognized	7,900,000	10,300,000
Sale of available-for-sale securities			211,600,000
Sale of available-for-sale securities, net of financing repayments			74,000,000
Gain from sale of available-for-sale securities			10,000,000
Available-for-sale security amount matured			27,100,000
Portion of securities with variable rate (as a percent)			100.00%	5.00%
Description of variable rate basis			LIBOR	LIBOR
Variable rate, weighted average spread (as a percent)			1.75%	1.30%
Estimated Fair Value
Securities within a loss less than 12 months			176,786,000
Unrealized Losses
Securities within a loss less than 12 months			(567,000)
Estimated Fair Value				19,023,000
Unrealized Losses				(683,000)
RMBS
Mortgage-Backed Securities Available-for-Sale
Purchases			161,204,000
Sales/Maturities			53,529,000
Principal payments received			69,466,000
Portion of securities with variable rate			154,700,000	120,700,000
Portion of securities with variable rate (as a percent)			93.80%	98.50%
Description of variable rate basis			LIBOR	LIBOR
Variable rate, weighted average spread (as a percent)			0.43%	0.31%
Maximum investment in available-for-sale securities with aggregate expected modified durations of less than 12 months (as a percent)			10.00%
Cost of third party management			700,000	400,000
Estimated Fair Value
Securities within a loss less than 12 months			70,103,000
Securities within a loss greater than 12 months			2,684,000
Unrealized Losses
Securities within a loss less than 12 months			(2,444,000)
Securities in a loss greater than 12 months			(399,000)
Estimated Fair Value				25,729,000
Unrealized Losses				$ (797,000)