Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (7,399)	$ (5,714)	$ (1,683)	$ 5,889
Foreign currency translation adjustments	(33,223)	27,504	(20,476)	33,569
Net change in:
Deferred losses on cash flow hedges, net of taxes of $(1,719), $1,632, $(1,632) and $1,920, respectively	4,549	(3,651)	2,747	(4,597)
Unrecognized retirement obligations, net of taxes of $(965), $(1,430), $(1,942) and $(2,677), respectively	3,021	2,479	6,096	4,553
Other comprehensive income (loss)	(25,653)	26,332	(11,633)	33,525
Comprehensive income (loss)	$ (33,052)	$ 20,618	$ (13,316)	$ 39,414