Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 1,245,343	$ 1,731,368
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	427,602	1,586,923
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	27,501	113,628
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	66,857	371,900
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	78,081	357,260
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	70,579	80,513
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	702	1,640
Mortgage Loan Purchase Commitments [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 2,943	$ 6,143