Derivative Instruments Derivative Instruments (Fair Value Hedge Attributable to Foreign Currency) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	$ 905	$ (3,755)	$ 7,441	$ 2,112
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	(905)	3,755	(7,441)	(2,112)
Gain (Loss) on Fair Value Hedge Ineffectiveness, Net	$ 0	$ 0	$ 0	$ 0