Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (21,541)	$ (177,604)	$ 7,914
Foreign currency translation adjustments	(6,724)	(27,783)	58,609
Net change in:
Deferred gains (losses) on cash flow hedges, net of taxes of $(737), $(2,353) and $1,930, respectively	2,117	6,291	(5,592)
Unrecognized retirement obligations, net of taxes of $(22,927), $(13,898) and $(6,293), respectively	64,151	47,025	10,914
Other comprehensive income	59,544	25,533	63,931
Comprehensive income (loss)	$ 38,003	$ (152,071)	$ 71,845