Postretirement Benefit Plans - Expense Related to Defined Benefit and Retiree Health Care Benefit Plans (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 | United States
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 5	$ 6	$ 10	$ 11
Interest cost	9	11	18	21
Expected return on plan assets	(10)	(10)	(21)	(20)
Recognized net actuarial loss	4	3	8	7
Amortization of prior service credit	0	0	0	0
Net periodic benefit costs	8	10	15	19
Settlement losses	0	4	2	10
Total, including other postretirement losses	8	14	17	29
Defined benefit plan | Non-U.S.
Defined Benefit Plan Disclosure [Line Items]
Service cost	9	9	18	18
Interest cost	11	11	23	22
Expected return on plan assets	(17)	(15)	(34)	(31)
Recognized net actuarial loss	6	7	11	14
Amortization of prior service credit	(1)	(1)	(1)	(1)
Net periodic benefit costs	8	11	17	22
Settlement losses	1	1	1	1
Total, including other postretirement losses	9	12	18	23
Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	1	1	2	2
Interest cost	3	5	7	9
Expected return on plan assets	(3)	(5)	(7)	(9)
Recognized net actuarial loss	0	1	1	2
Amortization of prior service credit	0	(1)	(1)	(2)
Net periodic benefit costs	1	1	2	2
Settlement losses	0	0	0	0
Total, including other postretirement losses	$ 1	$ 1	$ 2	$ 2
Defined Benefit Plan, Sponsor Location [Extensible List]	country:US	country:US	country:US	country:US