FAIR VALUE MEASUREMENTS Narrative (Details) - USD ($) $ in Billions |
9 Months Ended | |
|---|---|---|
Feb. 28, 2019 |
May 31, 2018 |
|
| Marketable security investments maturity information [Abstract] | ||
| Maturity of marketable security investments | As of February 28, 2019 and May 31, 2018, approximately 23% and 26%, respectively, of our marketable securities investments mature within one year and 77% and 74%, respectively, mature within one to five years. | |
| Percentage of marketable securities investments mature within one year | 23.00% | 26.00% |
| Percentage of marketable securities investments mature within one to five years | 77.00% | 74.00% |
| Senior notes [Member] | ||
| Marketable security investments maturity information [Abstract] | ||
| Total debt, carrying value | $ 56.0 | $ 58.0 |
| Fair Value Measurements Using Input Types Level 2 [Member] | Senior notes [Member] | ||
| Marketable security investments maturity information [Abstract] | ||
| Total debt, fair value | $ 56.9 | $ 59.0 |