Pension, Savings and Other Postretirement Benefit Plans - Defined Benefit Pension Cost (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
U.S.
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	$ 1	$ 1
Interest cost	40	40
Expected return on plan assets	(55)	(60)
Amortization of net losses	28	28
Net periodic pension cost	14	9
Non-U.S.
Defined Benefit Plan, Net Periodic Benefit Cost
Service cost	7	7
Interest cost	18	17
Expected return on plan assets	(18)	(19)
Amortization of net losses	7	8
Net periodic pension cost	$ 14	$ 13