Derivative Instruments Derivative Instruments (Fair Value Hedge Attributable to Foreign Currency) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Change in Unrealized Gain (Loss) on Fair Value Hedging Instruments	[1]	$ (11,164)	$ 9,456	$ (1,700)
Change in Unrealized Gain (Loss) on Hedged Item in Fair Value Hedge	[1]	$ 12,446	$ (9,456)	$ 1,700

[1] The net amount represents the ineffective portion of the fair value hedges.