Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 1,864,665	$ 2,463,892
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,910,985	1,080,772
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	117,304	112,641
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	439,070	880,682
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	441,866	865,600
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	86,601	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	$ 5,926	$ 2,093