Common Stock and Stock-Based Compensation - Total Stock-Based Compensation Expense (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense				$ 116	$ 92
Class B Common Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		$ 62	$ 49	116	92
Class B Common Stock | Stock Incentive Plan | Employee Stock Option
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	[1]	45	35	84	65
Accelerated stock option expense		8	5	14	9
Class B Common Stock | Stock Incentive Plan | Restricted stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense		9	8	17	15
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		$ 8	$ 6	$ 15	$ 12

[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 $8 million and $5 million for the three month periods ended November 30, 2015 and 2014, respectively, and $14 million and $9 million for the six month periods ended November 30, 2015 and 2014, respectively.