Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 1,731,368	$ 2,463,892
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,586,923	1,080,772
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	113,628	112,641
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	371,900	880,682
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	357,260	865,600
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	80,513	107,448
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,640	1,554
Mortgage Loan Purchase Commitments [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 6,143	$ 2,093