Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2016	Dec. 31, 2015
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 1,948,286	$ 2,463,892
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	2,168,110	1,080,772
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	112,441	112,641
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	521,057	880,682
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	591,422	865,600
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	91,825	107,448
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,555	1,554
Mortgage Loan Purchase Commitments [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 8,013	$ 2,093