Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Immediate Recognition of Actuarial Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Other Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Settlement and Curtailment Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Amortization of Prior Service Cost (Credit), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other income/(loss), net
Worldwide OPEB
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	$ 6	$ 5
Interest cost	57	58
Expected return on assets	0	0
Amortization of prior service costs/(credits)	2	1
Net remeasurement (gain)/loss	0	0
Defined Benefit Plan, Other Cost (Credit)	0	0
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	65	64
UNITED STATES \| Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	73	72
Interest cost	400	408
Expected return on assets	(455)	(486)
Amortization of prior service costs/(credits)	23	0
Net remeasurement (gain)/loss	0	113
Defined Benefit Plan, Other Cost (Credit)	8	2
Settlements and curtailments	0	42
Net periodic benefit cost/(income)	49	151
Foreign Plan \| Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	63	61
Interest cost	235	237
Expected return on assets	(255)	(219)
Amortization of prior service costs/(credits)	6	5
Net remeasurement (gain)/loss	(11)	0
Defined Benefit Plan, Other Cost (Credit)	14	4
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	$ 52	$ 88

Amount of gain (loss), recognized immediately as component of net periodic benefit (cost) credit, for change in value of benefit obligation or plan assets from experience different from that assumed, change in actuarial assumption, or consequence of temporarily deviating from substantive plan. Includes, but is not limited to, amount in excess of 10 percent of greater of fair value of plan assets or benefit obligation.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 45
-Paragraph 3A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480535/715-20-45-3A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (h)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)(4)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480506/715-20-50-6