Retirement-Related Benefits - Contributions and Direct Benefit Payments (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2021 |
Dec. 31, 2020 |
|
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | $ 2,085 | $ 2,066 |
| Contributions by employer - Noncash | 424 | 288 |
| Non-U.S. DB plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 86 | 166 |
| Multi-employer plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 17 | 23 |
| DC plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 992 | 1,015 |
| Direct Benefit Payments | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 671 | 538 |
| Nonpension Postretirement Plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 319 | 325 |
| Nonpension Postretirement Plans | Non-U.S. DB plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Contributions by employer - Noncash | $ 416 | $ 452 |