Retirement Plans - Summary of Net Pension Income or Postretirement Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Post-Retirement Life Insurance Plan
Net pension expense (income)
Service cost	$ 1	$ 1	$ 2
Interest cost	122	170	156
Amortization of unrecognized loss	(84)	(166)	(46)
Net expense	$ 39	$ 5	$ 112
Benefit obligation assumptions:
Discount rate	2.27%	3.09%	4.26%
Pension income/expense assumptions:
Discount rate	3.09%	4.26%	3.59%
United States
Net pension expense (income)
Service cost	$ 0	$ 0	$ 0
Interest cost	5,773	7,724	7,123
Expected return on plan assets	(9,817)	(12,187)	(12,898)
Amortization of unrecognized loss	6,488	5,246	5,863
Net expense	$ 2,444	$ 783	$ 88
Benefit obligation assumptions:
Discount rate	2.26%	3.15%	4.30%
Pension income/expense assumptions:
Discount rate	3.15%	4.30%	3.63%
Expected return on plan assets	3.76%	4.61%	4.72%
Foreign Plan
Net pension expense (income)
Service cost	$ 31	$ 37	$ 43
Interest cost	28	31	42
Expected return on plan assets	(16)	(17)	(25)
Amortization of unrecognized loss	174	170	162
Net expense	$ 217	$ 221	$ 222
Benefit obligation assumptions:
Discount rate	0.63%	1.00%	1.13%
Rate of compensation increase	3.00%	3.00%	3.00%
Pension income/expense assumptions:
Discount rate	0.63%	1.13%	1.38%
Expected return on plan assets	0.63%	1.13%	1.38%
Rate of compensation increase	3.00%	3.00%	2.00%