Retirement Benefits - Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Excluding Service Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net (Note 5)	Other income/(loss), net (Note 5)	Other income/(loss), net (Note 5)
Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), (Gain) Loss Due to Settlement, Curtailment, and Other	$ 240	$ 360	$ 544
Worldwide OPEB
Defined Benefit Plan Disclosure [Line Items]
Service cost	24	21	42
Interest cost	226	231	146
Expected return on assets	0	0	0
Amortization of prior service costs/(credits)	10	3	(3)
Net remeasurement (gain)/loss	(112)	286	(1,314)
Defined Benefit Plan, Other Cost (Credit)	0	1	0
Settlements and curtailments	0	0	(1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	148	542	(1,130)
Non-U.S. Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	248	245	416
Interest cost	938	965	504
Expected return on assets	(1,019)	(890)	(1,006)
Amortization of prior service costs/(credits)	25	22	22
Net remeasurement (gain)/loss	(1,019)	932	(436)
Defined Benefit Plan, Other Cost (Credit)	111	261	63
Settlements and curtailments	(22)	9	(2)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	(738)	1,544	(439)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain(Loss) Due to Curtailments and Other	89	268	57
U.S. Plans | Pension Plan
Defined Benefit Plan Disclosure [Line Items]
Service cost	288	292	500
Interest cost	1,581	1,641	1,054
Expected return on assets	(1,817)	(1,897)	(2,569)
Amortization of prior service costs/(credits)	92	0	2
Net remeasurement (gain)/loss	444	841	1,720
Defined Benefit Plan, Other Cost (Credit)	22	20	46
Settlements and curtailments	129	69	438
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)	$ 739	966	1,191
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement		$ (71)	$ (438)