Mortgage Securities - VIE's and CDO's (Details) (Variable Interest Entity, Primary Beneficiary [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Dec. 31, 2011
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Size/Principal outstanding	$ 5,641,902	[1]			$ 6,265,564	[1]
Assets on Balance Sheet	4,120	[2]			3,878	[2]
Liabilities on Balance Sheet	0				0
Maximum exposure to loss	4,120	[3]			3,878	[3]
Year to date loss on sale	0				0
Year to date cash flows	$ 4,030	[4]	$ 5,061	[4]

[1] Size/Principal Outstanding reflects the estimated principal of the underlying assets held by the VIE.

[2] Assets on balance sheet are securities issued by the entity and are recorded in the mortgage securities line item of the condensed consolidated balance sheets.

[3] The maximum exposure to loss includes the assets held by the Company. The maximum exposure to loss assumes a total loss on the referenced assets held by the VIE.

[4] Year to date cash flows are for the nine months ended September 30, 2012 and 2011, respectively.