Retirement Plans - Components of Prepaid (Accrued) Cost (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Retirement Plans
Prepaid pension asset	$ 56,642	$ 62,082
Post-Retirement Life Insurance Plan
Retirement Plans
Accrued expenses and other liabilities	(451)	(393)
Long-term pension obligations	(4,924)	(4,373)
Components of prepaid (accrued) cost, net	(5,375)	(4,766)
United States
Retirement Plans
Prepaid pension asset	56,642	62,082
Accrued expenses and other liabilities	(100)	(100)
Long-term pension obligations	(1,072)	(1,045)
Components of prepaid (accrued) cost, net	55,470	60,937
Foreign Plan
Retirement Plans
Prepaid pension asset	0	0
Accrued expenses and other liabilities	0	0
Long-term pension obligations	(1,091)	(1,214)
Components of prepaid (accrued) cost, net	$ (1,091)	$ (1,214)