Pension and Postretirement Benefit Plans - Pension Asset Fair Values (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	$ 6,341	$ 5,891
Defined Benefit Plan Assets, Excluding Reconciling Items | Level 1 | International
Benefit Plan Information
Fair value of plan assets	490	554
Defined Benefit Plan Assets, Excluding Reconciling Items | Level 2 | International
Benefit Plan Information
Fair value of plan assets	4,149	3,896
Defined Benefit Plan Assets, Excluding Reconciling Items | Level 3 | International
Benefit Plan Information
Fair value of plan assets	588	447
Defined Benefit Plan Assets, Excluding Reconciling Items | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	1,315	1,269
Defined Benefit Plan Assets, Excluding Reconciling Items | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	6,542	6,166
Equities | Level 1 | International
Benefit Plan Information
Fair value of plan assets	226	288
Equities | Level 2 | International
Benefit Plan Information
Fair value of plan assets	513	252
Equities | Level 3 | International
Benefit Plan Information
Fair value of plan assets	1	2
Equities | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	45	1
Equities | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	785	543
Fixed income | Level 1 | International
Benefit Plan Information
Fair value of plan assets	148	134
Fixed income | Level 2 | International
Benefit Plan Information
Fair value of plan assets	3,501	3,542
Fixed income | Level 3 | International
Benefit Plan Information
Fair value of plan assets	2	4
Fixed income | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	719	623
Fixed income | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	4,370	4,303
Private equity | Level 1 | International
Benefit Plan Information
Fair value of plan assets	0	2
Private equity | Level 2 | International
Benefit Plan Information
Fair value of plan assets	58	50
Private equity | Level 3 | International
Benefit Plan Information
Fair value of plan assets	2	2
Private equity | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	361	384
Private equity | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	421	438
Absolute return | Level 1 | International
Benefit Plan Information
Fair value of plan assets	10	8
Absolute return | Level 2 | International
Benefit Plan Information
Fair value of plan assets	1	1
Absolute return | Level 3 | International
Benefit Plan Information
Fair value of plan assets	583	439
Absolute return | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	189	259
Absolute return | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	783	707
Cash and cash equivalents | Level 1 | International
Benefit Plan Information
Fair value of plan assets	106	122
Cash and cash equivalents | Level 2 | International
Benefit Plan Information
Fair value of plan assets	76	51
Cash and cash equivalents | Level 3 | International
Benefit Plan Information
Fair value of plan assets	0	0
Cash and cash equivalents | Investments Measured at Net Asset Value | International
Benefit Plan Information
Fair value of plan assets	1	2
Cash and cash equivalents | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	183	175
Other items to reconcile to fair value of plan assets | Levels 1, 2 and 3 | International
Benefit Plan Information
Fair value of plan assets	(201)	(275)
U.S. Pension Plans | United States
Benefit Plan Information
Fair value of plan assets	12,348	12,648	$ 16,953
U.S. Pension Plans | International
Benefit Plan Information
Fair value of plan assets	6,341	5,891	8,016
U.S. Pension Plans | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	12,348	12,648
U.S. Pension Plans | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	2,407	2,234
U.S. Pension Plans | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	6,511	5,909
U.S. Pension Plans | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Defined Benefit Plan Assets, Excluding Reconciling Items | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	3,867	4,645
U.S. Pension Plans | Defined Benefit Plan Assets, Excluding Reconciling Items | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	12,785	12,788
U.S. Pension Plans | Equities | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	1,246	871
U.S. Pension Plans | Equities | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Equities | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Equities | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	174	271
U.S. Pension Plans | Equities | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	1,420	1,142
U.S. Pension Plans | Fixed income | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	1,153	1,354
U.S. Pension Plans | Fixed income | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	6,428	5,803
U.S. Pension Plans | Fixed income | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Fixed income | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	16	91
U.S. Pension Plans | Fixed income | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	7,597	7,248
U.S. Pension Plans | Private equity | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Private equity | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Private equity | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Private equity | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	1,622	1,700
U.S. Pension Plans | Private equity | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	1,622	1,700
U.S. Pension Plans | Absolute return | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	1	1
U.S. Pension Plans | Absolute return | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	83	85
U.S. Pension Plans | Absolute return | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Absolute return | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	1,314	1,794
U.S. Pension Plans | Absolute return | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	1,398	1,880
U.S. Pension Plans | Cash and cash equivalents | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	7	8
U.S. Pension Plans | Cash and cash equivalents | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	21
U.S. Pension Plans | Cash and cash equivalents | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
U.S. Pension Plans | Cash and cash equivalents | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	741	789
U.S. Pension Plans | Cash and cash equivalents | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	748	818
U.S. Pension Plans | Other items to reconcile to fair value of plan assets | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	(437)	(140)
Postretirement Benefits
Benefit Plan Information
Fair value of plan assets	980	1,017	$ 1,353
Postretirement Benefits | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	980	1,017
Postretirement Benefits | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	245	285
Postretirement Benefits | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	508	467
Postretirement Benefits | Defined Benefit Plan Assets, Excluding Reconciling Items | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Defined Benefit Plan Assets, Excluding Reconciling Items | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	256	271
Postretirement Benefits | Defined Benefit Plan Assets, Excluding Reconciling Items | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	1,009	1,023
Postretirement Benefits | Equities | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	118	168
Postretirement Benefits | Equities | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Equities | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Equities | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	11	16
Postretirement Benefits | Equities | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	129	184
Postretirement Benefits | Fixed income | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	92	96
Postretirement Benefits | Fixed income | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	503	461
Postretirement Benefits | Fixed income | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Fixed income | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	1	5
Postretirement Benefits | Fixed income | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	596	562
Postretirement Benefits | Private equity | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Private equity | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Private equity | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Private equity | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	108	99
Postretirement Benefits | Private equity | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	108	99
Postretirement Benefits | Absolute return | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Absolute return | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	5	5
Postretirement Benefits | Absolute return | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Absolute return | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	87	105
Postretirement Benefits | Absolute return | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	92	110
Postretirement Benefits | Cash and cash equivalents | Level 1 | United States
Benefit Plan Information
Fair value of plan assets	35	21
Postretirement Benefits | Cash and cash equivalents | Level 2 | United States
Benefit Plan Information
Fair value of plan assets	0	1
Postretirement Benefits | Cash and cash equivalents | Level 3 | United States
Benefit Plan Information
Fair value of plan assets	0	0
Postretirement Benefits | Cash and cash equivalents | Investments Measured at Net Asset Value | United States
Benefit Plan Information
Fair value of plan assets	49	46
Postretirement Benefits | Cash and cash equivalents | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	84	68
Postretirement Benefits | Other items to reconcile to fair value of plan assets | Levels 1, 2 and 3 | United States
Benefit Plan Information
Fair value of plan assets	$ (29)	$ (6)