Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 1,252,413	$ 1,731,368
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	398,587	1,586,923
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	29,747	113,628
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	74,900	371,900
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	64,425	357,260
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	70,510	80,513
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,229	1,640
Mortgage Loan Purchase Commitments [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 5,150	$ 6,143