Postretirement Benefit Plans - Expense Related to Defined Benefit and Retiree Health Care Benefit Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 18	$ 18	$ 19
Interest cost	31	38	35
Expected return on plan assets	(36)	(41)	(42)
Amortization of prior service cost (credit)	0	0	0
Recognized net actuarial loss	7	9	17
Net periodic benefit costs	20	24	29
Settlement losses	16	10	23
Total, including other postretirement losses	36	34	52
U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	3	3	5
Interest cost	13	14	15
Expected return on plan assets	(12)	(14)	(15)
Amortization of prior service cost (credit)	(2)	(1)	(3)
Recognized net actuarial loss	0	0	2
Net periodic benefit costs	2	2	4
Settlement losses	0	0	0
Total, including other postretirement losses	2	2	4
Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	34	31	36
Interest cost	38	43	45
Expected return on plan assets	(78)	(86)	(67)
Amortization of prior service cost (credit)	1	1	(1)
Recognized net actuarial loss	14	29	20
Net periodic benefit costs	9	18	33
Settlement losses	1	3	3
Total, including other postretirement losses	$ 10	$ 21	$ 36