FAIR VALUE MEASUREMENTS Narrative (Details) - USD ($) $ in Billions	3 Months Ended
	Aug. 31, 2017	May 31, 2017
Marketable security investments maturity information [Abstract]
Maturity of marketable security investments	As of August 31, 2017 and May 31, 2017, approximately 28% and 32%, respectively, of our marketable securities investments mature within one year and 72% and 68%, respectively, mature within one to six years.
Percentage of marketable securities investments mature within one year	28.00%	32.00%
Percentage of marketable securities investments mature within one to six years	72.00%	68.00%
Short and Long Term Debt [Abstract]
Senior notes	$ 53.1	$ 54.0
Fair Value Measurements Using Input Types Level 2 [Member]
Liabilities [Abstract]
Total debt fair value	$ 55.9	$ 56.5