Postretirement Benefit Plans - Expense Related to Defined Benefit and Retiree Health Care Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 19	$ 22	$ 22
Interest cost	35	42	42
Expected return on plan assets	(42)	(41)	(41)
Amortization of prior service credit	0	0	0
Recognized net actuarial loss	17	14	21
Net periodic benefit costs	29	37	44
Settlement losses	23	36	21
Total, including other postretirement losses	52	73	65
United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5	5
Interest cost	15	17	20
Expected return on plan assets	(15)	(17)	(20)
Amortization of prior service credit	(3)	(4)	(3)
Recognized net actuarial loss	2	3	7
Net periodic benefit costs	4	4	9
Settlement losses	0	0	0
Total, including other postretirement losses	$ 4	$ 4	$ 9
Defined Benefit Plan, Sponsor Location [Extensible List]	country:US	country:US	country:US
Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 36	$ 37	$ 34
Interest cost	45	44	52
Expected return on plan assets	(67)	(62)	(68)
Amortization of prior service credit	(1)	(2)	(2)
Recognized net actuarial loss	20	28	25
Net periodic benefit costs	33	45	41
Settlement losses	3	2	2
Total, including other postretirement losses	$ 36	$ 47	$ 43