Retirement Plans and Postretirement Medical Benefits (Components of Net Periodic Benefit Cost for Defined Benefit Pension Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Document Fiscal Year Focus	2019
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 967	$ 1,405	$ 1,727
Interest cost	6,584	6,640	7,100
Amortization of prior service (credit) cost	321	304	297
Amortization of net actuarial loss	2,026	3,048	3,600
Curtailment	0	246	0
Net periodic benefit (income) cost	9,898	11,643	12,724
United States | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	83	92	132
Interest cost	63,171	61,490	68,611
Expected return on plan assets	(92,726)	(101,087)	(97,656)
Amortization of net transition asset	0	0	0
Amortization of prior service (credit) cost	(60)	(60)	(60)
Amortization of net actuarial loss	26,146	31,298	28,954
Special termination benefits	0	0	0
Settlements and curtailments	2,381	44,665	0
Net periodic benefit (income) cost	(1,005)	36,398	(19)
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Service cost	1,543	2,159	2,274
Interest cost	17,853	18,089	18,836
Expected return on plan assets	(34,363)	(35,687)	(32,242)
Amortization of net transition asset	(6)	(7)	(8)
Amortization of prior service (credit) cost	243	(71)	(71)
Amortization of net actuarial loss	6,337	7,264	8,052
Special termination benefits	0	208	0
Settlements and curtailments	397	(13)	0
Net periodic benefit (income) cost	$ (7,996)	$ (8,058)	$ (3,159)