Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (177,604)	$ 7,914	$ 21,554
Foreign currency translation adjustments	(27,783)	58,609	(27,407)
Net change in:
Deferred gains (losses) on cash flow hedges, net of taxes of $(2,353), $1,930 and $(335), respectively	6,291	(5,592)	1,725
Unrecognized retirement obligations, net of taxes of $(13,898), $(6,293) and $(7,247), respectively	47,025	10,914	11,562
Other comprehensive income (loss)	25,533	63,931	(14,120)
Comprehensive income (loss)	$ (152,071)	$ 71,845	$ 7,434