Pension, Other Postretirement Benefits and Savings Plans - Amounts Recognized in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Other Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	$ (27)	$ (59)
Net actuarial loss	47	68
Gross amount recognized	20	9
Deferred income taxes	(26)	(20)
Minority shareholders’ equity	0	0
Net amount recognized	(6)	(11)
United States | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	(4)	(4)
Net actuarial loss	2,603	2,615
Gross amount recognized	2,599	2,611
Deferred income taxes	(103)	(118)
Minority shareholders’ equity	0	0
Net amount recognized	2,496	2,493
Non-U.S. | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Prior service (credit) cost	4	1
Net actuarial loss	669	685
Gross amount recognized	673	686
Deferred income taxes	(109)	(115)
Minority shareholders’ equity	(1)	0
Net amount recognized	$ 563	$ 571