Retirement Plans (Details 2) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Nov. 30, 2016 |
Nov. 30, 2015 |
Nov. 30, 2016 |
Nov. 30, 2015 |
|
| Pension Plans | ||||
| Net Periodic Benefit Cost | ||||
| Service cost | $ 180 | $ 165 | $ 360 | $ 331 |
| Interest cost | 293 | 295 | 586 | 590 |
| Expected return on plan assets | (386) | (377) | (772) | (754) |
| Amortization of prior service credit and other | (29) | (29) | (58) | (60) |
| Total net periodic benefit cost | 58 | 54 | 116 | 107 |
| Postretirement Healthcare Plans | ||||
| Net Periodic Benefit Cost | ||||
| Service cost | 9 | 10 | 18 | 20 |
| Interest cost | 10 | 10 | 20 | 21 |
| Total net periodic benefit cost | $ 19 | $ 20 | $ 38 | $ 41 |