Post-Employment Benefits - Benefit Obligation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Plan assets at fair value:
Plan assets at fair value, balance at the beginning of the year	$ 12,371
Plan assets at fair value, balance at the end of the year	13,838	$ 12,371
Projected benefit obligations greater than plan assets
Projected benefit obligations greater than plan assets, December 31	(1,554)	(2,773)
Long-term liabilities	(2,738)	(3,119)
Benefit obligations
Accumulated benefit obligations	11,500	11,900
Accumulated benefit obligations, the projected benefit obligations and the aggregate plan assets
Projected benefit obligation	2,632	8,946
Fair value of plan assets	1,057	7,010
Accumulated benefit obligation	1,406	2,459
Projected benefit obligation	1,554	2,773
Fair value of plan assets	136	965
Defined Benefit Plans
Projected benefit obligations:
Projected benefit obligations, balance at the beginning of the year	13,129	11,238
Service cost - benefits earned during the year	391	336	$ 250
Interest cost on projected benefit obligations	248	300	337
(Gains) losses, primarily changes in discount rates, plan design changes, law changes and differences between actual and estimated health care costs	(463)	1,305
Benefits paid	(340)	(327)
Other, including foreign currency translation	(192)	277
Projected benefit obligations, balance at the end of the year	12,773	13,129	11,238
Plan assets at fair value:
Plan assets at fair value, balance at the beginning of the year	12,018	10,277
Actual return (loss) on plan assets	1,521	1,463
Company contributions	418	400
Benefits paid	(340)	(327)
Other, including foreign currency translation	(149)	205
Plan assets at fair value, balance at the end of the year	13,468	12,018	10,277
Projected benefit obligations greater than plan assets
Projected benefit obligations less (greater) than plan assets, December 31	695
Projected benefit obligations greater than plan assets, December 31		(1,111)
Long-term assets	2,270	824
Short-term liabilities	(31)	(29)
Long-term liabilities	(1,544)	(1,906)
Net liability	695	(1,111)
Amounts Recognized in Accumulated Other Comprehensive Income (loss):
Actuarial losses, net	3,062	4,559
Prior service cost (credits)	(5)	(5)
Total	3,057	4,554
Accumulated benefit obligations, the projected benefit obligations and the aggregate plan assets
Projected benefit obligation		1,111
Defined Benefit Plans | Non-US
Benefit obligations
Projected benefit obligations	3,700	4,100
Medical and Dental Plans
Projected benefit obligations:
Projected benefit obligations, balance at the beginning of the year	1,567	1,556
Service cost - benefits earned during the year	56	46	23
Interest cost on projected benefit obligations	33	42	52
(Gains) losses, primarily changes in discount rates, plan design changes, law changes and differences between actual and estimated health care costs	(16)	(5)
Benefits paid	(74)	(73)
Other, including foreign currency translation		1
Projected benefit obligations, balance at the end of the year	1,566	1,567	1,556
Plan assets at fair value:
Plan assets at fair value, balance at the beginning of the year	353	360
Actual return (loss) on plan assets	56	46
Company contributions	35	20
Benefits paid	(74)	(73)
Plan assets at fair value, balance at the end of the year	370	353	$ 360
Projected benefit obligations greater than plan assets
Projected benefit obligations greater than plan assets, December 31	(1,196)	(1,214)
Short-term liabilities	(2)	(1)
Long-term liabilities	(1,194)	(1,213)
Net liability	(1,196)	(1,214)
Amounts Recognized in Accumulated Other Comprehensive Income (loss):
Actuarial losses, net	412	486
Prior service cost (credits)	(39)	(67)
Total	373	419
Accumulated benefit obligations, the projected benefit obligations and the aggregate plan assets
Projected benefit obligation	$ 1,196	$ 1,214