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

Maturity of marketable security investments

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Percentage of marketable securities investments mature within one to five years.

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Percentage of marketable securities investments mature within one year.

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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