Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 29, 2012	Feb. 28, 2011	Feb. 29, 2012	Feb. 28, 2011	May 31, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]
Available-for-sale securities with maturity dates within one year from purchase date	$ 848		$ 848		$ 2,253
Available-for-sale securities with maturity dates over one year and less than five years from purchase date	328		328		330
Interest income related to cash and equivalents and short-term investments	7	8	22	23
Fair value of long term debt	$ 281		$ 281		$ 482