Fair Value Measurements - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2011	Nov. 30, 2010	Nov. 30, 2011	Nov. 30, 2010	May 31, 2011
Fair Value, Measurement Inputs, Disclosure [Line Items]
Available-for-sale securities with maturity dates within one year	$ 1,098		$ 1,098		$ 2,253
Available-for-sale securities with maturity dates over one year and less than five years	338		338		330
Fair value of long term debt	354		354		482
Interest income related to cash and equivalents and short-term investments	$ 7	$ 8	$ 15	$ 16