Other Income (expense) - (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Other Income And Expenses [Abstract]
Income from third party license fees	$ 208	$ 193	$ 512	$ 413
Foreign exchange (losses) gains, net	(2,004)	(144)	(1,183)	(381)
Gain on fixed asset disposals, net	(83)	30	(81)	39
Non-income tax refunds and other related credits	832	813	2,131	965
Pension and post retirement benefit costs, non-service components	(341)	(895)	(23,866)	(1,791)
Other Operating Income (Expense) Net	395	46	319	163
Total other income (expense), net	$ (993)	$ 43	(22,168)	$ (592)
Defined Benefit Plan Settlement Charge			$ 22,700