Retirement Plans - Net Pension Income Domestic and Foreign (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Plans
Net pension expense (income)
Total expense, net	$ 666	$ 249	$ 1,330	$ 499
UNITED STATES
Net pension expense (income)
Service cost	0	0	0	0
Interest cost	1,443	1,931	2,886	3,862
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(2,454)	(3,047)	(4,908)	(6,094)
Amortization of loss	1,622	1,311	3,244	2,623
Total expense, net	611	195	1,222	391
Foreign Plan [Member]
Net pension expense (income)
Service cost	8	9	15	18
Interest cost	6	7	13	15
Defined Benefit Plan, Expected Return (Loss) on Plan Assets	(3)	(4)	(7)	(9)
Amortization of loss	44	42	87	84
Total expense, net	$ 55	$ 54	$ 108	$ 108