Pension, Savings and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined contribution savings plan, contribution expense recognized	$ 28	$ 28	$ 57	$ 58
Postretirement benefits expense (credit)	3	$ (1)	6	$ (3)
Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Contributions to pension plans	8		19
Minimum | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded pension plans in current year	25		25
Maximum | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded pension plans in current year	$ 50		$ 50