Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net Income	$ 41,899	$ 35,227	$ 76,598
Other comprehensive gain (loss), gross of tax:
Net gain (loss) on pension benefit obligations	91	244	(675)
Foreign currency translation adjustments	(19,212)	48,059	(16,678)
Unrealized gain (loss) on foreign currency derivative securities	1,096	301	(1,395)
Unrealized gain (loss) on commodity derivative securities	(218)	55	743
Other comprehensive gain (loss), gross of tax	(18,243)	48,659	(18,005)
Other comprehensive gain (loss), related tax effects:
Cumulative effect of accounting change due to ASU 2018-02	(40)
Net gain (loss) on pension benefit obligations	(15)	(60)	185
Foreign currency translation adjustments	(390)	148	297
Unrealized gain (loss) on foreign currency derivative securities	(300)	(81)	375
Unrealized gain (loss) on commodity derivative securities	(68)	(19)	(273)
Other comprehensive gain (loss), related tax effect	(813)	(12)	584
Other comprehensive loss, net of tax:	(19,056)	48,647	(17,421)
Comprehensive income:	$ 22,843	$ 83,874	$ 59,177