Financial Derivatives Financial Derivatives (Schedule of Derivative Activity) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Interest Rate Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 2,227,315	$ 828,442
Credit Default Swap [Member]
Derivative [Line Items]
Average Monthly Notional Amount	552,411	319,603
Total Return Swaps [Member]
Derivative [Line Items]
Average Monthly Notional Amount	55,108	29,212
Futures [Member]
Derivative [Line Items]
Average Monthly Notional Amount	738,830	134,831
Option contract [Member]
Derivative [Line Items]
Average Monthly Notional Amount	926,369	10,736
Forwards [Member]
Derivative [Line Items]
Average Monthly Notional Amount	42,143	369
Warrant [Member]
Derivative [Line Items]
Average Monthly Notional Amount	$ 120	$ 0