FAIR VALUE MEASUREMENTS (Details) (USD $) In Millions, unless otherwise specified	Feb. 28, 2013	May 31, 2012
Assets [Abstract]
U.S. Treasury, U.S. government and U.S. government agency debt securities	$ 120	$ 100
Commercial paper debt securities	15,619	13,954
Corporate debt securities and other	4,550	2,237
Derivative financial instruments	50	69
Total assets	20,339	16,360
Liabilities [Abstract]
Contingent consideration	269	387
Total debt	19,800	16,500
Fair Value Measurements Using Input Types Level 1 [Member]
Assets [Abstract]
U.S. Treasury, U.S. government and U.S. government agency debt securities	120	100
Corporate debt securities and other	199	254
Total assets	319	354
Fair Value Measurements Using Input Types Level 2 [Member]
Assets [Abstract]
Commercial paper debt securities	15,619	13,954
Corporate debt securities and other	4,351	1,983
Derivative financial instruments	50	69
Total assets	20,020	16,006
Liabilities [Abstract]
Total debt fair value	22,300	19,300
Fair Value Measurements Using Input Types Level 3 [Member]
Liabilities [Abstract]
Contingent consideration	$ 269	$ 387