Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income	$ 65,091	$ 63,809	$ 62,560
Other comprehensive income (loss):
Foreign currency translation adjustment	1,766	(3,241)	3,150
Cumulative effect of accounting change	0	(350)	0
Adjustment to pension and post-retirement benefit liability, net of tax	77	723	205
Other comprehensive income (loss)	1,843	(2,868)	3,355
Total comprehensive income	$ 66,934	$ 60,941	$ 65,915