Shareholders' Equity Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Before-tax amount [Abstract]
Foreign currency translation adjustment	$ (34,271)	$ 20,520	$ (17,978)	$ 35,586
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	3,068	(634)	4,504	(537)
Net hedging (gain) loss reclassified into net income	(2,354)	259	(2,373)	637
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	409	418	829	824
Total other comprehensive income (loss), before tax	(33,148)	20,563	(15,018)	36,510
Tax (provision) benefit [Abstract]
Foreign currency translation adjustment	111	(73)	118	(123)
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	(173)	244	(426)	207
Net hedging (gain) loss reclassified into net income	(55)	(100)	(50)	(246)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(8)	(225)	(14)	(230)
Total other comprehensive income (loss) tax benefit	(125)	(154)	(372)	(392)
Net-of-tax amount [Abstract]
Foreign currency translation adjustment	(34,160)	20,447	(17,860)	35,463
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	2,895	(390)	4,078	(330)
Net hedging loss (gain) reclassified into net income	(2,409)	159	(2,423)	391
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, after Tax	401	193	815	594
Total other comprehensive income (loss), net of tax	$ (33,273)	$ 20,409	$ (15,390)	$ 36,118