Retirement Benefits - Expense (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Worldwide OPEB
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	$ 10	$ 12
Interest cost	37	32
Expected return on assets	0	0
Amortization of prior service costs/(credits)	(1)	(3)
Net remeasurement (gain)/loss	0	0
Defined Benefit Plan, Other Cost (Credit)	0	0
Settlements and curtailments	0	0
Net periodic benefit cost/(income)	46	41
Foreign Plan | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	111	144
Interest cost	134	99
Expected return on assets	(268)	(285)
Amortization of prior service costs/(credits)	7	5
Net remeasurement (gain)/loss	0	(484)
Defined Benefit Plan, Other Cost (Credit)	7	37
Settlements and curtailments	0	1
Net periodic benefit cost/(income)	(9)	(483)
Foreign Plan | Pension Plan | Global Redesign
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) due to Settlement, Curtailment, and Other	7	38
UNITED STATES | Pension Plan
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)
Service cost	125	138
Interest cost	263	223
Expected return on assets	(642)	(702)
Amortization of prior service costs/(credits)	0	1
Net remeasurement (gain)/loss	0	423
Defined Benefit Plan, Other Cost (Credit)	4	2
Settlements and curtailments	0	39
Net periodic benefit cost/(income)	$ (250)	$ 124