Pension, Savings and Other Postretirement Benefit Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Defined contribution savings plan, contribution expense recognized	$ 29	$ 30
Postretirement benefits credit	3	$ (2)
Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Contributions to pension plans	11
Minimum | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded pension plans in current year	25
Maximum | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Expected contribution to funded pension plans in current year	$ 50