Retirement Plans - Net Pension Income Domestic and Foreign (Details) - Pension Plans - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Net pension expense (income)
Total expense, net	$ 666	$ 250	$ 1,996	$ 749
UNITED STATES
Net pension expense (income)
Service cost	0	0	0	0
Interest cost	1,443	1,931	4,329	5,793
Expected return on plan assets	(2,454)	(3,046)	(7,362)	(9,140)
Amortization of loss	1,622	1,311	4,866	3,934
Total expense, net	611	196	1,833	587
Foreign Plan
Net pension expense (income)
Service cost	8	9	23	27
Interest cost	6	8	19	23
Expected return on plan assets	(3)	(4)	(10)	(13)
Amortization of loss	44	41	131	125
Total expense, net	$ 55	$ 54	$ 163	$ 162