Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Nov. 30, 2016	Nov. 30, 2015	Nov. 30, 2016	Nov. 30, 2015	May 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Interest income	$ 5,000,000	$ 2,000,000	$ 9,000,000	$ 4,000,000
Fair value transfers between fair value hierarchy levels			0		$ 0
Available-for-sale Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale securities with maturity dates within one year from purchase date	1,369,000,000		1,369,000,000
Available-for-sale securities with maturity dates over one year and less than five years from purchase date	$ 235,000,000		$ 235,000,000