Postretirement Benefit Plans - Plan Assets by Level Three Hierarchy (Details) - USD ($) $ in Millions		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 1,061	$ 987	$ 869
U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		389	356	330
Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		3,008	2,661	$ 2,410
Other | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	1,061	987
Other | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	360	294
Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	2,748	2,433
Level 1 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 1 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		29	62
Level 1 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		112	100
Level 2 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 2 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 2 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		148	128
Fixed income securities and cash equivalents | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		743	640
Fixed income securities and cash equivalents | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		251	230
Fixed income securities and cash equivalents | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,278	1,947
Fixed income securities and cash equivalents | Other | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	743	640
Fixed income securities and cash equivalents | Other | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	222	168
Fixed income securities and cash equivalents | Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	2,063	1,762
Fixed income securities and cash equivalents | Level 1 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 1 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		29	62
Fixed income securities and cash equivalents | Level 1 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		69	59
Fixed income securities and cash equivalents | Level 2 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 2 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 2 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		146	126
Equity securities | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		318	347
Equity securities | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		138	126
Equity securities | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		730	714
Equity securities | Other | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	318	347
Equity securities | Other | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	138	126
Equity securities | Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	685	671
Equity securities | Level 1 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 1 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 1 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		43	41
Equity securities | Level 2 | U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 2 | U.S. | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 2 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 2	$ 2

[1] Consists of bond index and equity index funds, measured at net asset value per share, as well as cash equivalents.