Retirement-Related Benefits - Cost of Pension Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Cost/(Income) of Pension Plans
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	$ 456	$ 600	$ 934	$ 1,219
U.S. | Pension Plans
Cost/(Income) of Pension Plans
Interest cost	$ 302	$ 277	$ 603	$ 555
Interest cost - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ (475)	$ (451)	$ (950)	$ (901)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 2	$ 4	$ 4	$ 8
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 179	$ 249	$ 359	$ 498
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Other costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 8	$ 80	$ 15	$ 160
Cost of defined contribution plans	141	151	282	302
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	149	231	298	462
U.S. | Nonpension Postretirement Plans
Cost/(Income) of Pension Plans
Service cost	1	2	2	4
Interest cost	$ 18	$ 16	$ 37	$ 32
Interest cost - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 1	$ 1	$ 2	$ 2
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 2	$ 13	$ 4	$ 26
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 23	$ 32	$ 46	$ 64
Non-US | Pension Plans
Cost/(Income) of Pension Plans
Service cost	59	68	123	133
Interest cost	$ 131	$ 108	$ 270	$ 216
Interest cost - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ (259)	$ (279)	$ (532)	$ (559)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 3	$ (5)	$ 7	$ (7)
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 260	$ 352	$ 537	$ 708
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Curtailments and settlements	$ 11	$ 16	$ 19	$ 34
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Multi-employer plans	$ 3	$ 5	$ 7	$ 11
Other costs/(credits)	$ 6	$ 3	$ 15	$ 15
Other costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 215	$ 268	$ 446	$ 551
Cost of defined contribution plans	92	101	190	206
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	307	369	636	757
Non-US | Nonpension Postretirement Plans
Cost/(Income) of Pension Plans
Service cost	1	1	2	2
Interest cost	$ 9	$ 8	$ 18	$ 16
Interest cost - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ (1)	$ (1)	$ (1)	$ (2)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 0	$ 0	$ 0	$ 0
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 1	$ 4	$ 2	$ 8
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Curtailments and settlements		$ 0		$ 0
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 10	$ 13	$ 20	$ 25