Pensions Benefit Plans and Other Postretirement Benefits - Funded Status (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefit Plans | Minimum
Defined Benefit Plan Disclosure
Percentage of pension plan assets	10.00%
U.S. | Pension Benefit Plans
Defined Benefit Plan Disclosure
Plan assets at fair value	$ 1,094	$ 1,394	$ 1,654
Postretirement benefit obligations	(1,413)	(1,650)	(1,956)
Plan assets less than projected benefit obligations	(319)	(256)
Items not yet recognized in pension expense and net postretirement benefit cost:
Actuarial gain (loss)	785	811
Prior service cost (credit)		1
Total	785	812
Net amount recognized	466	556
U.S. | Other Postretirement Benefits
Defined Benefit Plan Disclosure
Postretirement benefit obligations	(74)	(89)	(92)
Items not yet recognized in pension expense and net postretirement benefit cost:
Actuarial gain (loss)	(8)	(19)
Prior service cost (credit)	15	22
Total	7	3
Net amount recognized	(67)	(86)
Non-U.S. | Pension Benefit Plans
Defined Benefit Plan Disclosure
Plan assets at fair value	843	975	1,011
Postretirement benefit obligations	(1,022)	(1,148)	(1,235)
Plan assets less than projected benefit obligations	(179)	(173)
Items not yet recognized in pension expense and net postretirement benefit cost:
Actuarial gain (loss)	285	284
Prior service cost (credit)	4	(2)
Total	289	282
Net amount recognized	110	109
Non-U.S. | Other Postretirement Benefits
Defined Benefit Plan Disclosure
Postretirement benefit obligations	(80)	(89)	$ (81)
Items not yet recognized in pension expense and net postretirement benefit cost:
Actuarial gain (loss)	(2)	(7)
Total	(2)	(7)
Net amount recognized	$ (82)	$ (96)