Pension, Other Postretirement Benefits and Savings Plans - Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	$ (32)	$ (27)
Net actuarial loss	25	47
Gross amount recognized	(7)	20
Deferred income taxes	(19)	(26)
Minority shareholders’ equity	0	0
Net amount recognized	(26)	(6)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	(3)	(4)
Net actuarial loss	2,493	2,603
Gross amount recognized	2,490	2,599
Deferred income taxes	(77)	(103)
Minority shareholders’ equity	0	0
Net amount recognized	2,413	2,496
Non-U.S. | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	31	4
Net actuarial loss	611	669
Gross amount recognized	642	673
Deferred income taxes	(105)	(109)
Minority shareholders’ equity	(1)	(1)
Net amount recognized	$ 536	$ 563