Retirement Plans - Net Pension Income or Postretirement Expense (Details 6) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Post-Retirement Life Insurance Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 407
Net pension expense (income)
Service cost	2	$ 2	$ 3
Interest cost	156	161	207
Defined Benefit Plan, Amortization of Gain (Loss)	46	101	149
Net expense (income)	$ 112	$ 62	$ 61
Benefit obligation assumptions:
Discount rate	4.26%	3.59%	4.10%
Rate of compensation increase	0.00%	0.00%	0.00%
Pension income/expense assumptions:
Discount rate	3.59%	4.10%	4.43%
Rate of compensation increase	0.00%	0.00%	0.00%
Foreign Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 52
Net pension expense (income)
Service cost	43	$ 48	$ 51
Interest cost	42	34	46
Expected return on plan assets	(25)	(20)	(26)
Defined Benefit Plan, Amortization of Gain (Loss)	(162)	(155)	(140)
Settlement loss	0	0	0
Net expense (income)	$ 222	$ 217	$ 211
Benefit obligation assumptions:
Discount rate	1.13%	1.38%	1.13%
Rate of compensation increase	3.00%	2.00%	2.00%
Pension income/expense assumptions:
Discount rate	1.38%	1.13%	1.63%
Expected return on plan assets	1.38%	1.13%	1.63%
Rate of compensation increase	2.00%	2.00%	2.00%
Domestic Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Expected Future Benefit Payment, Next Twelve Months	$ 15,537
Net pension expense (income)
Service cost	0	$ 0	$ 87
Interest cost	7,123	8,273	11,024
Expected return on plan assets	(12,898)	(16,243)	(18,976)
Defined Benefit Plan, Amortization of Gain (Loss)	(5,863)	(5,785)	(5,994)
Settlement loss	0	13,476	0
Net expense (income)	$ 88	$ 11,291	$ (1,871)
Benefit obligation assumptions:
Discount rate	4.30%	3.63%	4.16%
Rate of compensation increase	0.00%	0.00%	0.00%
Pension income/expense assumptions:
Discount rate	3.63%	4.16%	4.43%
Expected return on plan assets	4.72%	5.61%	6.63%
Rate of compensation increase	0.00%	0.00%	0.00%