Retirement Plans and Postretirement Medical Benefits (Pretax Amounts Recognized in AOCI) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 41,570	$ 33,272
Prior service (credit) cost	129	502
Total	41,699	33,774
United States | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	783,211	772,850
Prior service (credit) cost	(209)	(270)
Transition asset	0	0
Total	783,002	772,580
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	334,520	315,319
Prior service (credit) cost	8,072	8,317
Transition asset	(7)	(11)
Total	$ 342,585	$ 323,625