Derivative Financial Instruments (Schedule of Notional Amounts of Outstanding Derivative Positions) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Amount	$ 5,514,013	$ 10,327,833
Interest Rate Contract [Member]
Derivative [Line Items]
Notional Amount	5,366,372	10,237,325
Other Contract [Member]
Derivative [Line Items]
Notional Amount	12,858	60
Credit Default Swap, Selling Protection [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Notional Amount	92,985	55,626
Credit Default Swap, Buying Protection [Member] | Credit Risk Contract [Member]
Derivative [Line Items]
Notional Amount	$ 41,798	$ 34,822