Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Feb. 29, 2016	Feb. 28, 2015	Feb. 29, 2016	Feb. 28, 2015	May. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Available-for-sale securities with maturity dates within one year from purchase date	$ 1,830,000,000		$ 1,830,000,000
Available-for-sale securities with maturity dates over one year and less than five years from purchase date	232,000,000		232,000,000
Interest income	4,000,000	$ 1,000,000	8,000,000	$ 4,000,000
Fair value transfers between fair value hierarchy levels			0
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Outstanding receivables	$ 0		$ 0		$ 150,000,000