CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income	$ 49,317	$ 37,187	$ 46,259
Other comprehensive income (loss):
Change in pension plans, net of income taxes of $409, $1,409, and $55, respectively	2,016	(2,400)	(90)
Foreign currency translation adjustments	25,664	(10,965)	(10,334)
Unrealized gain on hedging activities, net of tax	122	0	0
Total other comprehensive income (loss), net of tax	27,802	(13,365)	(10,424)
Comprehensive income	$ 77,119	$ 23,822	$ 35,835