Employee Benefit Plans - Assumed health care cost trend rates (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
May 31, 2026 |
May 31, 2025 |
May 31, 2024 |
|
| Assumed health care cost trend rates [Abstract] | |||
| Health care cost trend rate assumed for the next fiscal year | 7.50% | 6.30% | |
| Rate to which the cost trend is assumed to decline (the ultimate trend rate) | 5.00% | 5.00% | |
| Defined Benefit Plan, Year Health Care Cost Trend Rate Reaches Ultimate Trend Rate | 2037 | 2031 | |
| Cumulative reduction of its accumulated post-retirement benefit obligation | $ 0.1 | $ 0.1 | |