Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income	$ 19,913	$ 22,837	$ 26,258	$ 31,189
Other comprehensive income (loss):
Foreign currency translation adjustment	998	(1,787)	1,840	(1,677)
Cumulative effect of accounting change	0	0	0	(350)
Minimum pension and post retirement benefit plan adjustments	12	26	24	53
Other comprehensive income (loss)	1,010	(1,761)	1,864	(1,974)
Total comprehensive income	$ 20,923	$ 21,076	$ 28,122	$ 29,215