Retirement-Related Benefits - Contributions and Direct Benefit Payments (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | $ 2,177 | $ 2,288 |
| Contributions by employer - Noncash | 635 | 598 |
| Multi-employer Plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 32 | 38 |
| Non-U.S. DB plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 243 | 325 |
| Nonpension Postretirement Plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 304 | 335 |
| DC plans | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | 1,040 | 1,024 |
| Direct Benefit Payments | ||
| Defined Benefit Plan Disclosure [Line Items] | ||
| Total | $ 559 | $ 567 |