Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2014	Feb. 28, 2013	Feb. 28, 2014	Feb. 28, 2013	May 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale securities with maturity dates within one year from purchase date	$ 2,303		$ 2,303		$ 2,229
Available-for-sale securities with maturity dates over one year and less than five years from purchase date	862		862		399
Interest income related to cash and equivalents and short-term investments	3	6	9	20
Fair Value, Measurements, Recurring | Fair Value Measurements Using Level 2
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Fair value of long term debt	$ 1,131		$ 1,131		$ 1,219