Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 12,105	$ 19,601	$ 17,994	$ 37,734
Foreign currency translation adjustments	16,559	(1,530)	50,128	(2,975)
Net change in:
Deferred (gains) losses on cash flow hedges, net of taxes of $111, $289, $2,031 and $88, respectively	(1,514)	(858)	(6,111)	152
Unrecognized retirement obligations net of taxes of $(1,340), $(1,405), $(4,018) and $(4,214), respectively	2,285	2,319	6,838	6,957
Other comprehensive income (loss)	17,330	(69)	50,855	4,134
Comprehensive income	$ 29,435	$ 19,532	$ 68,849	$ 41,868