Other Comprehensive Loss - After-tax Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 87,861	$ 128,885	$ 128,688	$ 109,596
Net current period change	2,564	(5,998)	(2,888)	(4,249)
Ending balance	95,345	130,788	95,345	130,788
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(24,032)	(22,847)
Net current period change			(257)	(3,048)
Ending balance	(24,289)	(25,895)	(24,289)	(25,895)
Derivative instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			464	496
Net current period change			(781)	(193)
Ending balance	(317)	303	(317)	303
Pension and post-retirement benefits plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(22,382)	(25,120)
Amortization of actuarial losses			(1,850)	(1,008)
Ending balance	(24,232)	(26,128)	(24,232)	(26,128)
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(51,402)	(45,722)	(45,950)	(47,471)
Ending balance	$ (48,838)	$ (51,720)	$ (48,838)	$ (51,720)