Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2015	Nov. 30, 2014	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	$ 2,020,000,000		$ 2,020,000,000
Available-for-sale securities with maturity dates over one year and less than five years from purchase date	245,000,000		245,000,000
Interest income	2,000,000	$ 2,000,000	4,000,000	$ 3,000,000
Fair value of long term debt	2,020,000,000		2,020,000,000		$ 1,160,000,000
Fair value transfers between fair value hierarchy levels			0
Assets, fair value disclosure, nonrecurring	0		0		0
Liabilities, fair value disclosure, nonrecurring	0		0		0
Prepaid Expenses and Other Current Assets
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Outstanding receivables	150,000,000		150,000,000		150,000,000
Foreign exchange forwards and options
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative liability, fair value of collateral	0		0
Foreign exchange forwards and options | Cash and Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative liability, fair value of collateral					$ 0
Interest rate swap
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Derivative liability, fair value of collateral	$ 0		$ 0