Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 19,601	$ 13,504	$ 37,734	$ 30,277
Foreign currency translation adjustments	(1,530)	(3,262)	(2,975)	(27,895)
Net change in:
Deferred (gains) losses on cash flow hedges, net of taxes of $289, $1,045, $88 and $938, respectively	(858)	(2,823)	152	(2,558)
Unrecognized retirement obligations, net of taxes of $(1,405), $(1,895), $(4,214) and $(5,675), respectively	2,319	3,083	6,957	9,253
Other comprehensive income (loss)	(69)	(3,002)	4,134	(21,200)
Comprehensive income	$ 19,532	$ 10,502	$ 41,868	$ 9,077