Retirement Plans and Postretirement Medical Benefits (Pretax Amounts Recognized in AOCI) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Nonpension postretirement benefit plans
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	$ 28,368	$ 43,160
Prior service credit	823	1,466
Total	29,191	44,626
United States | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	809,836	835,265
Prior service credit	(330)	(391)
Transition asset	0	0
Total	809,506	834,874
Foreign | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Net actuarial loss	318,474	321,914
Prior service credit	8,496	(597)
Transition asset	(17)	(24)
Total	$ 326,953	$ 321,293