Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 2,463,892	$ 2,227,315
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,080,772	552,411
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	112,641	55,108
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	880,682	738,830
Options [Member]
Derivative [Line Items]
Average Monthly Notional Amount	865,600	926,369
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	107,448	42,143
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	1,554	120
Mortgage Loan Purchase Commitments [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 2,093	$ 0