Common Stock and Stock-Based Compensation - Stock Option Transactions Under Plan (Detail) - Stock Incentive Plan 1990 - $ / shares shares in Millions		12 Months Ended
		May. 31, 2015	May. 31, 2014	May. 31, 2013
Options Outstanding - Shares
Beginning Balance (in shares)	[1]	63.5	67.7	64.3
Exercised (in shares)	[1]	(13.6)	(11.0)	(9.9)
Forfeited (in shares)	[1]	(1.0)	(1.3)	(1.3)
Granted (in shares)	[1]	9.2	8.1	14.6
Ending Balance (in shares)	[1]	58.1	63.5	67.7
Options exercisable (in shares)	[1]	34.3	37.0	35.9
Options Outstanding - Weighted-Average Option Price
Beginning Balance (in dollars per share)		$ 39.28	$ 34.72	$ 30.59
Exercised (in dollars per share)		30.78	28.29	24.70
Forfeited (in dollars per share)		59.02	48.33	40.14
Granted (in dollars per share)		77.68	63.54	46.55
Ending Balance (in dollars per share)		47.00	39.28	34.72
Options exercisable (in dollars per share)		$ 36.53	$ 31.42	$ 27.70

[1] Includes stock appreciation rights transactions.