Total Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Nov. 30, 2011		Nov. 30, 2010		Nov. 30, 2011		Nov. 30, 2010
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock Options	$ 26	[1]	$ 21	[1]	$ 44	[1]	$ 35	[1]
ESPPs	5		4		8		8
Restricted Stock	5		4		9		7
Total stock-based compensation expense	$ 36		$ 29		$ 61		$ 50

[1] Expense for stock options includes the expense associated with stock appreciation rights. Accelerated stock option expense is recorded for employees eligible for accelerated stock option vesting upon retirement. Accelerated stock option expense was $4 million for both the three month periods ended November 30, 2011 and 2010, and $8 million and $6 million for the six month periods ended November 30, 2011 and 2010, respectively.