Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Worldwide OPEB
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	$ 11	$ 12	$ 21	$ 24
Interest cost	37	32	74	64
Expected return on assets	0	0	0	0
Amortization of prior service costs/(credits)	0	(3)	(1)	(6)
Net remeasurement (gain)/loss	0	0	0	0
Defined Benefit Plan, Other Cost (Credit)	(1)	0	(1)	0
Settlements and curtailments	0	0	0	0
Net periodic benefit cost/(income)	47	41	93	82
UNITED STATES | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	125	127	250	265
Interest cost	264	239	527	462
Expected return on assets	(643)	(664)	(1,285)	(1,366)
Amortization of prior service costs/(credits)	1	0	1	1
Net remeasurement (gain)/loss	0	(182)	0	241
Defined Benefit Plan, Other Cost (Credit)	7	3	11	5
Settlements and curtailments	0	10	0	49
Net periodic benefit cost/(income)	(246)	(467)	(496)	(343)
Foreign Plan | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	107	139	218	283
Interest cost	133	109	267	208
Expected return on assets	(259)	(284)	(527)	(569)
Amortization of prior service costs/(credits)	5	7	12	12
Net remeasurement (gain)/loss	16	(81)	16	(565)
Defined Benefit Plan, Other Cost (Credit)	10	47	17	84
Settlements and curtailments	0	(1)	0	0
Net periodic benefit cost/(income)	12	(64)	3	(547)
Foreign Plan | Pension Plan | Global Redesign
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Defined Benefit Plan, Other Cost (Credit)	$ 9	$ 46	$ 16	$ 84