Retirement Plans - Summary of Accumulated Other Comprehensive loss (Details) - Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Post-Retirement Life Insurance Plan
Accumulated Other Comprehensive Loss
Beginning balance	$ (608)	$ (849)
Amortization of retirement benefits, net of tax	64	129
Net actuarial (loss) gain	493	112
Ending balance	(51)	(608)
Net actuarial (loss) gain	493	112
United States
Accumulated Other Comprehensive Loss
Beginning balance	88,830	95,494
Amortization of retirement benefits, net of tax	(4,995)	(4,060)
Net actuarial (loss) gain	7,402	(2,604)
Foreign exchange impact	0	0
Ending balance	91,237	88,830
Net actuarial (loss) gain	7,402	(2,604)
Foreign Plan
Accumulated Other Comprehensive Loss
Beginning balance	1,900	1,916
Amortization of retirement benefits, net of tax	(146)	(138)
Net actuarial (loss) gain	14	78
Foreign exchange impact	133	44
Ending balance	1,901	1,900
Net actuarial (loss) gain	$ 14	$ 78