Retirement-Related Benefits - All Retirement Plans Cost (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2021 |
Jun. 30, 2020 |
Jun. 30, 2021 |
Jun. 30, 2020 |
|
| Retirement-Related Benefits | ||||
| Defined benefit and contribution pension plans - cost | $ 653 | $ 596 | $ 1,325 | $ 1,179 |
| Nonpension postretirement plans - cost | 45 | 50 | 89 | 102 |
| Total | $ 698 | $ 645 | $ 1,414 | $ 1,281 |
| Year-to-year percent change, defined benefit and contribution pension plans cost (as a percent) | 9.60% | 12.40% | ||
| Year-to-year percent change, nonpension postretirement plans cost (as a percent) | (10.40%) | (12.50%) | ||
| Year-to-year percent change, total (as a percent) | 8.10% | 10.40% | ||