Retirement Plans - Schedule of Retirement Plan Costs (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Feb. 28, 2021 |
Feb. 29, 2020 |
Feb. 28, 2021 |
Feb. 29, 2020 |
|
| Pension And Other Postretirement Benefit Expense [Abstract] | ||||
| Defined benefit pension plans, net | $ 20 | $ 38 | $ 72 | $ 112 |
| Defined contribution plans | 182 | 147 | 493 | 425 |
| Postretirement healthcare plans | 21 | 21 | 62 | 64 |
| Retirement plan mark-to-market (“MTM”) net loss | 52 | |||
| Retirement plans costs | $ 223 | $ 206 | $ 679 | $ 601 |