Retirement-Related Benefits - Cost of Pension Plans (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cost/(Income) of Pension Plans
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	$ 478	$ 619
U.S. | Pension Plans
Cost/(Income) of Pension Plans
Interest cost	$ 302	$ 277
Interest cost - income statement location	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ (475)	$ (451)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 2	$ 4
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 179	$ 249
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense
Other costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 8	$ 80
Cost of defined contribution plans	141	151
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	149	231
U.S. | Nonpension Postretirement Plans
Cost/(Income) of Pension Plans
Service cost	1	2
Interest cost	$ 18	$ 16
Interest cost - income statement location	Other (income) and expense	Other (income) and expense
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 1	$ 1
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 2	$ 13
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 23	$ 32
Non-U.S. | Pension Plans
Cost/(Income) of Pension Plans
Service cost	64	65
Interest cost	$ 139	$ 108
Interest cost - income statement location	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ (274)	$ (279)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 4	$ (2)
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 278	$ 356
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense
Curtailments and settlements	$ 8	$ 17
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense
Multi-employer plans	$ 4	$ 6
Other costs/(credits)	$ 9	$ 11
Other costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 231	$ 283
Cost of defined contribution plans	98	105
Total defined benefit and contribution pension plans cost recognized in the Consolidated Income Statement	328	388
Non-U.S. | Nonpension Postretirement Plans
Cost/(Income) of Pension Plans
Service cost	1	1
Interest cost	$ 9	$ 8
Interest cost - income statement location	Other (income) and expense	Other (income) and expense
Expected return on plan assets	$ 0	$ (1)
Expected return on plan assets - income statement location	Other (income) and expense	Other (income) and expense
Amortization of prior service costs/(credits)	$ 0	$ 0
Amortization of prior service costs/(credits) - income statement location	Other (income) and expense	Other (income) and expense
Recognized actuarial losses	$ 1	$ 4
Recognized actuarial losses - income statement location	Other (income) and expense	Other (income) and expense
Curtailments and settlements - income statement location	Other (income) and expense	Other (income) and expense
Total net periodic pension / nonpension (income)/cost of defined benefit plans	$ 10	$ 12