Retirement Plans - Net Pension Income Domestic and Foreign (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plans
Net pension expense (income)
(Income) expense, net	$ 250	$ 79
Foreign Plan [Member]
Net pension expense (income)
Service cost	9	11
Interest cost	7	11
Defined Benefit Plan, Expected Return on Plan Assets, Net of Expenses	(4)	(7)
Amortization of loss	42	42
(Income) expense, net	54	57
Domestic Plan [Member]
Net pension expense (income)
Interest cost	1,931	1,781
Defined Benefit Plan, Expected Return on Plan Assets, Net of Expenses	(3,047)	(3,225)
Amortization of loss	1,312	1,466
(Income) expense, net	$ 196	$ 22