Pension and Postretirement Benefits - Accumulated Benefit Obligation in Excess of Plan Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Domestic Plans | Funded Plans
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation	$ 16,331	$ 15,572
Accumulated benefit obligation	16,331	15,572
Fair value of plan assets	11,878	11,291
Domestic Plans | Unfunded Pension Plans
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation	9,776	9,462
Accumulated benefit obligation	9,776	9,454
Foreign Pension Plans | Funded Plans
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation	10,916	9,990
Accumulated benefit obligation	10,447	9,347
Fair value of plan assets	10,798	10,013
Foreign Pension Plans | Unfunded Pension Plans
Accumulated benefit obligation in excess of plan assets
Projected benefit obligation	2,449	2,331
Accumulated benefit obligation	$ 2,449	$ 2,331