Other Comprehensive (Income) Loss - After-tax Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 102,615	$ 96,926	$ 95,370	$ 128,688
Net current period change	1,798	2,578	(414)	(5,452)
Ending balance	111,637	87,861	111,637	87,861
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(19,024)	(24,032)
Net current period change			(584)	(2,885)
Ending balance	(19,608)	(26,917)	(19,608)	(26,917)
Pension and post-retirement benefits plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(27,423)	(22,382)
Amortization of actuarial gain (loss)			673	(893)
Ending balance	(26,750)	(23,275)	(26,750)	(23,275)
Derivative instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			1,441	464
Net current period change			(503)	(1,674)
Ending balance	938	(1,210)	938	(1,210)
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(47,218)	(53,980)	(45,006)	(45,950)
Ending balance	$ (45,420)	$ (51,402)	$ (45,420)	$ (51,402)