Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
Nov. 30, 2016 |
Nov. 30, 2015 |
Nov. 30, 2016 |
Nov. 30, 2015 |
May 31, 2016 |
|
| Accumulated Other Comprehensive Income Loss Net Of Tax [Abstract] | |||||
| Foreign currency translation gain (loss): Beginning balance | $ (502) | $ (391) | $ (514) | $ (253) | |
| Translation adjustment | (230) | (33) | (218) | (171) | |
| Foreign currency translation gain (loss): Ending balance | (732) | (424) | (732) | (424) | |
| Retirement plans adjustments: Beginning Balance | 326 | 401 | 345 | 425 | |
| Reclassification from AOCI | 19 | 18 | 38 | 42 | |
| Retirement plans adjustments: Ending Balance | 307 | 383 | 307 | 383 | |
| Accumulated other comprehensive (loss) income at end of period | (425) | (41) | (425) | (41) | $ (169) |
| Amortization of retirement plans prior service credits, before tax | 30 | 29 | 60 | 60 | |
| Income tax benefit | (11) | (11) | (22) | (18) | |
| AOCI reclassifications, net of tax | $ 19 | $ 18 | $ 38 | $ 42 | |