Retirement-Related Benefits - Cost of Pension Plans (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Cost/(Income) of Pension Plans
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	$ 259	$ 456	$ 541	$ 934
U.S. Plans | Pension Plan
Cost/(Income) of Pension Plans
Service cost	0	0	0	0
Interest cost	272	302	545	603
Expected return on plan assets	(382)	(475)	(764)	(950)
Amortization of prior service costs/(credits)	0	2	0	4
Recognized actuarial losses	27	179	55	359
Curtailments and settlements	0	0	0	0
Multi-employer plans	0	0	0	0
Other costs/(credits)	0	0	0	0
Total net periodic pension (income)/cost of defined benefit plans	(82)	8	(165)	15
Cost of defined contribution plans	151	141	323	282
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	69	149	158	298
U.S. Plans | Other Postretirement Benefits Plan
Cost/(Income) of Pension Plans
Service cost	1	1	2	2
Interest cost	29	18	58	37
Expected return on plan assets	0	0	0	0
Amortization of prior service costs/(credits)	(7)	1	(15)	2
Recognized actuarial losses	0	2	0	4
Curtailments and settlements	0	0	0	0
Total net periodic pension (income)/cost of defined benefit plans	23	23	46	46
Non-U.S. Plans | Pension Plan
Cost/(Income) of Pension Plans
Service cost	44	59	88	123
Interest cost	292	131	580	270
Expected return on plan assets	(362)	(259)	(718)	(532)
Amortization of prior service costs/(credits)	5	3	10	7
Recognized actuarial losses	101	260	203	537
Curtailments and settlements	6	11	5	19
Multi-employer plans	3	3	6	7
Other costs/(credits)	10	6	19	15
Total net periodic pension (income)/cost of defined benefit plans	99	215	194	446
Cost of defined contribution plans	91	92	188	190
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	190	307	382	636
Non-U.S. Plans | Other Postretirement Benefits Plan
Cost/(Income) of Pension Plans
Service cost	1	1	1	2
Interest cost	10	9	19	18
Expected return on plan assets	(1)	(1)	(1)	(1)
Amortization of prior service costs/(credits)	0	0	0	0
Recognized actuarial losses	0	1	(1)	2
Curtailments and settlements	0	0	0	0
Total net periodic pension (income)/cost of defined benefit plans	$ 10	$ 10	$ 19	$ 20