Derivative Instruments (Current Period Cash Flow Hedges in AOCI (loss) before Taxes) (Details) - Cash Flow Hedging [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Derivative Instruments, Gain (Loss) [Line Items]
Balance, Beginning of Period	$ (31,591)	$ (4,578)	$ 403
Derivative Instruments, Gain (Loss) Recognized in Other Comprehensive Income (Loss), Effective Portion, Net	2,676	(25,801)	(3,969)
Balance, End of Period	(29,397)	(31,591)	(4,578)
Gain (Loss) on Investments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	(87)	0
Investment Income [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ 569	$ 1,212	$ 1,012