Retirement Plans and Postretirement Medical Benefits (Other Changes in Plan Assets and Benefit Obligations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	$ 11,496	$ 6,931
Amortization of net actuarial loss	(3,198)	(2,026)
Amortization of prior service credit (cost)	(373)	(321)
Total recognized in other comprehensive income	7,925	4,584
United States | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	44,216	(8,459)
Amortization of net actuarial loss	(32,490)	(26,146)
Amortization of prior service credit (cost)	60	60
Net transition asset	0	0
Settlements and curtailments	(1,364)	(2,381)
Total recognized in other comprehensive income	10,422	(36,926)
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial (gain) loss	32,103	3,643
Amortization of net actuarial loss	(7,842)	(6,337)
Amortization of prior service credit (cost)	(245)	(243)
Net transition asset	4	6
Settlements and curtailments	(5,060)	(397)
Total recognized in other comprehensive income	$ 18,960	$ (3,328)