Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income	$ 25,949	$ 27,292	$ 38,711	$ 39,351
Other comprehensive income (loss):
Foreign currency translation adjustment	761	2,815	3,959	(3,083)
Minimum post retirement benefit plan adjustments	27	18	54	36
Other comprehensive income (loss)	788	2,833	4,013	(3,047)
Total comprehensive income	$ 26,737	$ 30,125	$ 42,724	$ 36,304