Stock-Based Compensation - Total Stock-Based Compensation Expense (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Feb. 28, 2015		Feb. 28, 2014		Feb. 28, 2015		Feb. 28, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense					$ 140		$ 131
Class B Common Stock | Stock Incentive Plan 1990
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	48		43		140		131
Class B Common Stock | Stock Incentive Plan 1990 | Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	35	[1]	32	[1]	100	[1]	93	[1]
Class B Common Stock | Stock Incentive Plan 1990 | ESPPs
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	5		5		17		16
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		$ 6		$ 23		$ 22

[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 February 28, 2015 and 2014 was $5 million and $3 million, respectively, and for the nine month periods ended February 28, 2015 and 2014 was $14 million and $11 million, respectively.