Retirement Plans and Postretirement Medical Benefits (Pension Plans with an Accumulated Benefit Obligation in Excess of Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Document Fiscal Year Focus	2019
Fair value of plan assets	$ 516,000	$ 426,000
United States
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	1,612,745	1,500,680
Accumulated benefit obligation	1,612,241	1,500,231
Fair value of plan assets	1,486,325	1,326,296
Foreign
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation	615,288	540,798
Accumulated benefit obligation	614,293	538,666
Fair value of plan assets	$ 516,634	$ 426,446