Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income	$ 64,566	$ 65,091	$ 63,809
Other comprehensive income (loss):
Foreign currency translation adjustment	3,301	1,766	(3,241)
Cumulative effect of accounting change	0	0	(350)
Adjustment to pension and post-retirement benefit liability, net of tax	(371)	77	723
Other comprehensive income (loss)	2,930	1,843	(2,868)
Total comprehensive income	$ 67,496	$ 66,934	$ 60,941