Common Stock and Stock-Based Compensation - Total Stock-Based Compensation Expense (Detail) - USD ($) $ in Millions		3 Months Ended
		Aug. 31, 2015	Aug. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		$ 54	$ 43
Class B Common Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		54	43
Class B Common Stock | Stock Incentive Plan 1990 | Employee Stock Option
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	[1]	39	30
Accelerated stock option expense		6	4
Class B Common Stock | Stock Incentive Plan 1990 | Restricted stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		8	7
Class B Common Stock | Employee Stock Purchase Plans | Employee Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		$ 7	$ 6

[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 for the three month periods ended August 31, 2015 and 2014 was $6 million and $4 million, respectively.