Postretirement Benefit Plans - Plan Assets by Level Three Hierarchy (Details) - USD ($) $ in Millions		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 869	$ 995	$ 1,034
United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		330	394	434
Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		2,410	2,593	$ 2,309
Other | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	869	995
Other | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	271	260
Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	2,190	2,363
Level 1 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 1 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		59	132
Level 1 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		80	23
Level 2 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 2 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	2
Level 2 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		140	206
Level 3 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 3 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Level 3 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	1
Fixed income securities and cash equivalents | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		563	654
Fixed income securities and cash equivalents | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		214	245
Fixed income securities and cash equivalents | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		1,788	1,845
Fixed income securities and cash equivalents | Other | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	563	654
Fixed income securities and cash equivalents | Other | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	155	111
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]	1,602	1,646
Fixed income securities and cash equivalents | Level 1 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 1 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		59	132
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		47	16
Fixed income securities and cash equivalents | Level 2 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 2 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	2
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		139	183
Fixed income securities and cash equivalents | Level 3 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 3 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Fixed income securities and cash equivalents | Level 3 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		306	341
Equity securities | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		116	149
Equity securities | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		622	747
Equity securities | Other | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	306	341
Equity securities | Other | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	116	149
Equity securities | Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]	588	717
Equity securities | Level 1 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 1 | United States | 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		33	7
Equity securities | Level 2 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 2 | United States | 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		1	23
Equity securities | Level 3 | United States | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 3 | United States | Retiree health care plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		0	0
Equity securities | Level 3 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 0	0
Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			1
Other | Other | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	[1]		0
Other | Level 1 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Other | Level 2 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			0
Other | Level 3 | Non-U.S. | Defined benefit plan
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets			$ 1

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