Other Comprehensive Loss - After-tax Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 96,926	$ 120,065	$ 128,688	$ 109,596
Net current period change	2,578	1,955	(5,452)	1,749
Ending balance	87,861	128,885	87,861	128,885
Foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(24,032)	(22,847)
Net current period change			(2,885)	338
Ending balance	(26,917)	(22,509)	(26,917)	(22,509)
Derivative instruments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			464	496
Net current period change			(1,674)	322
Ending balance	(1,210)	818	(1,210)	818
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			(893)	1,089
Ending balance	(23,275)	(24,031)	(23,275)	(24,031)
Accumulated other comprehensive loss
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(53,980)	(47,677)	(45,950)	(47,471)
Ending balance	$ (51,402)	$ (45,722)	$ (51,402)	$ (45,722)