Retirement Plans - Net Pension Income or Postretirement Expense (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Post-Retirement Life Insurance Plan
Net pension expense (income)
Service cost	$ 1	$ 2	$ 2
Interest cost	170	156	161
Defined Benefit Plan, Amortization of Gain (Loss)	166	46	101
Net expense (income)	$ 5	$ 112	$ 62
Benefit obligation assumptions:
Discount rate	3.09%	4.26%	3.59%
Pension income/expense assumptions:
Discount rate	4.26%	3.59%	4.10%
Foreign Plan
Net pension expense (income)
Service cost	$ 37	$ 43	$ 48
Interest cost	31	42	34
Expected return on plan assets	(17)	(25)	(20)
Defined Benefit Plan, Amortization of Gain (Loss)	(170)	(162)	(155)
Settlement loss	0	0	0
Net expense (income)	$ 221	$ 222	$ 217
Benefit obligation assumptions:
Discount rate	1.00%	1.13%	1.38%
Rate of compensation increase	3.00%	3.00%	2.00%
Pension income/expense assumptions:
Discount rate	1.13%	1.38%	1.13%
Expected return on plan assets	1.13%	1.38%	1.13%
Rate of compensation increase	3.00%	2.00%	2.00%
UNITED STATES
Net pension expense (income)
Service cost	$ 0	$ 0	$ 0
Interest cost	7,724	7,123	8,273
Expected return on plan assets	(12,187)	(12,898)	(16,243)
Defined Benefit Plan, Amortization of Gain (Loss)	(5,246)	(5,863)	(5,785)
Settlement loss	0	0	13,476
Net expense (income)	$ 783	$ 88	$ 11,291
Benefit obligation assumptions:
Discount rate	3.15%	4.30%	3.63%
Pension income/expense assumptions:
Discount rate	4.30%	3.63%	4.16%
Expected return on plan assets	4.61%	4.72%	5.61%