Other Income (expense) - (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Other Income And Expenses [Abstract]
Income from third party license fees	$ 190	$ 242	$ 702	$ 655
Foreign exchange (losses) gains, net	(1,897)	376	(3,080)	(5)
(Loss) gain on fixed asset disposals, net	(24)	72	(105)	111
Non-income tax refunds and other related credits	0	82	2,131	1,047
Pension and post retirement benefit income (costs), non-service components	1,375	(513)	(22,491)	(2,304)
Other operating income (expense), net	117	(56)	436	107
Total other income (expense), net	(239)	$ 203	(22,407)	$ (389)
Defined Benefit Plan Settlement Charge			22,700
Pension Premium Refund	$ 1,600		$ 1,600