Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ (95,831)	$ 12,105	$ (97,512)	$ 17,994
Foreign currency translation adjustments	(3,217)	16,559	(23,693)	50,128
Net change in:
Deferred gains (losses) on cash flow hedges, net of taxes of $(582), $111, $(1,718) and $2,031, respectively	1,616	(1,514)	4,363	(6,111)
Unrecognized retirement obligations, net of taxes of $(1,004), $(1,340), $(2,946) and $(4,018), respectively	21,572	2,285	27,668	6,838
Other comprehensive income	19,971	17,330	8,338	50,855
Comprehensive income (loss)	$ (75,860)	$ 29,435	$ (89,174)	$ 68,849

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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