Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 8,151	$ 18,785
Other comprehensive income, net of tax:
Currency translation adjustments (net of income tax of $0 in 2018 and 2017)	8,921	5,492
Change in unrecognized net periodic pension costs (net of income tax of $142 in 2018 and $226 in 2017)	380	236
Other (net of income tax of $0 in 2018 and 2017)	6	110
Total other comprehensive income, net of tax	9,307	5,838
Comprehensive income	$ 17,458	$ 24,623