CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 49,990	$ 47,319	$ 87,651
Foreign currency translation adjustment	24,907	(4,990)	(12,505)
Pension and other postretirement benefits:
Pension settlement (benefits) charges, net of tax (Note 4)	(48)	43,934	0
Actuarial net gain (loss) incurred, net of tax (Note 4)	1,255	(6,079)	(1,678)
Amortization of loss, net of tax (Note 4)	244	390	176
Derivative instrument designated as cash flow hedge:
Change in unrealized (loss) gain before reclassifications, net of tax (Note 4)	(1,504)	(1,171)	519
Unrealized loss (gain) reclassified into earnings, net of tax (Note 4)	2,476	(155)	(191)
Other comprehensive income (loss)	27,330	31,929	(13,679)
Comprehensive income	$ 77,320	$ 79,248	$ 73,972