Postretirement Benefit Plans - Expense Related to Defined Benefit and Retiree Health Care Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 22	$ 22	$ 22
Interest cost	42	42	43
Expected return on plan assets	(41)	(41)	(48)
Amortization of prior service cost (credit)	0	0	0
Recognized net actuarial loss	14	21	19
Net periodic benefit costs	37	44	36
Settlement losses	36	21	25
Total, including other postretirement losses	73	65	61
U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	5	5
Interest cost	17	20	20
Expected return on plan assets	(17)	(20)	(22)
Amortization of prior service cost (credit)	(4)	(3)	2
Recognized net actuarial loss	3	7	8
Net periodic benefit costs	4	9	13
Settlement losses	0	0	0
Total, including other postretirement losses	4	9	13
Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	37	34	35
Interest cost	44	52	53
Expected return on plan assets	(62)	(68)	(76)
Amortization of prior service cost (credit)	(2)	(2)	(2)
Recognized net actuarial loss	28	25	24
Net periodic benefit costs	45	41	34
Settlement losses	2	2	2
Total, including other postretirement losses	$ 47	$ 43	$ 36