Shareholders' Equity Schedule of Other Comprehensive Income (Loss) Tax Effect (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Before-tax amount [Abstract]
Foreign currency translation adjustment	$ 54,218	$ (23,280)	$ (74,219)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, before Tax	484	(1,407)	962
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	585	(1,768)	123
Net hedging (gain) loss reclassified into net income (loss)	916	1,322	1,639
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment and Tax	3,401	(6,256)	6,512
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, before Tax	1,782	2,752	2,459
Total other comprehensive income (loss), before tax	61,386	(28,637)	(62,524)
Tax (provision) benefit [Abstract]
Foreign currency translation adjustment	(364)	(290)	328
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Tax	0	0	0
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	(225)	681	(47)
Net hedging (gain) loss reclassified into net income (loss)	(353)	(510)	(629)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, Tax	(1,047)	65	(1,942)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Reclassification Adjustment from AOCI, Tax	(548)	(29)	(733)
Total other comprehensive income (loss) tax (provision) benefit	(2,537)	(83)	(3,023)
Net-of-tax amount
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent	53,854	(23,570)	(73,891)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax	484	(1,407)	962
Net unrealized gain (loss) on derivative instruments designated as cash flow hedges	360	(1,087)	76
Net hedging (gain) loss reclassified into net income (loss)	563	812	1,010
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	2,354	(6,191)	4,570
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax	1,234	2,723	1,726
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$ 58,849	$ (28,720)	$ (65,547)