Retirement Plans - Net Pension Expense Domestic and Foreign (Details) - Pension Plans - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net pension expense (income)
Total expense, net	$ 107,447		$ 666	$ 131,227	$ 1,996
UNITED STATES
Net pension expense (income)
Service cost	0		0	0	0
Interest cost	385		1,443	2,856	4,329
Expected return on plan assets	429		(2,454)	(1,742)	(7,362)
Amortization of loss	377		1,622	3,694	4,866
Settlement charges	106,206	$ 20,063	0	126,269	0
Total expense, net	107,397		611	131,077	1,833
Foreign Plan
Net pension expense (income)
Service cost	6		8	18	23
Interest cost	4		6	12	19
Expected return on plan assets	(3)		(3)	(9)	(10)
Amortization of loss	43		44	129	131
Settlement charges	0		0	0	0
Total expense, net	$ 50		$ 55	$ 150	$ 163