Retirement Plans - Net Pension Income Domestic and Foreign (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Plans
Net pension expense (income)
(Income) expense, net	$ 249	$ 78	$ 499	$ 157
Foreign Plan [Member]
Net pension expense (income)
Service cost	9	11	18	22
Interest cost	7	11	15	22
Defined Benefit Plan, Expected Return on Plan Assets, Net of Expenses	(4)	(6)	(9)	(13)
Amortization of loss	42	40	84	82
(Income) expense, net	54	56	108	113
Domestic Plan [Member]
Net pension expense (income)
Service cost			0	0
Interest cost	1,931	1,781	3,862	3,562
Defined Benefit Plan, Expected Return on Plan Assets, Net of Expenses	(3,047)	(3,225)	(6,094)	(6,450)
Amortization of loss	1,311	1,466	2,623	2,932
(Income) expense, net	$ 195	$ 22	$ 391	$ 44