Fair Value of Financial Instruments Level 3 (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2013 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Non-Agency CMBS [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Non-Agency RMBS [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Mar. 31, 2013 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2012 Other Investments [Member] Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at the beginning of the period		$ 105,245	$ 100,102	$ 5,118	$ 25	$ 25
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0	19,516	19,516	0
Unrealized (loss) gain included in OCI	0	(478)	(444)	(34)
Principal payments	0	3,404	2,059	1,345
Amortization	0	115	104	11
Balance at the end of the period		$ 120,994	$ 117,219	$ 3,750	$ 25	$ 25