Mortgage Securities - VIE's and CDO's (Details) (Variable Interest Entity, Primary Beneficiary [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Size/Principal outstanding	$ 4,062,068	[1]	$ 4,811,987	[1]
Assets on balance sheet	3,381	[2]	3,728	[2]
Liabilities on balance sheet	0		0
Maximum exposure to loss	3,381	[3]	3,728	[3]
Year to date loss on sale	0		0
Year to date cash flows	$ 7,136		$ 5,448

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

[2] Assets on balance sheet are securities issued by the entity and are recorded in the current marketable securities line item of the 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 securitization trust.