Long-Term Debt, Derivatives and Letters of Credit - Additional Information (Detail) € in Millions	6 Months Ended
	Nov. 30, 2015 USD ($)	Nov. 30, 2015 EUR (€)	May. 31, 2015 USD ($)
Standby Letters of Credit [Member]
Line of Credit Facility [Line Items]
Outstanding letter of credit	$ 13,200,000		$ 12,100,000
New Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity	$ 500,000,000
Maturity period	2020-07
Credit Facility, Covenant Terms	The New Credit Facility also contains financial covenants requiring the Company to maintain as of the end of each fiscal quarter (i) a maximum ratio of consolidated funded debt to consolidated EBITDA of not more than 4.00 to 1.00 (until August 31, 2016, at which point the ratio will decrease by 0.25 to 1.00 every other quarter until it reaches 3.00 to 1.00), (ii) a maximum ratio of senior secured debt to consolidated EBITDA of not more than 3.00 to 1.00 and (iii) an interest coverage ratio of less than 3.00 to 1.00.
Maximum ratio of consolidated funded debt to consolidated EBITDA	4.00	4.00
Decrease in ratio of consolidated funded debt to consolidated EBITDA	0.25
Maximum ratio of senior secured debt to consolidated EBITDA	3.00	3.00
Minimum interest coverage ratio	3.00	3.00
New Credit Facility [Member] | Five-year revolving loan facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity	$ 300,000,000
New Credit Facility [Member] | Five-year term loan facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity	200,000,000
Net Investment Hedge [Member]
Line of Credit Facility [Line Items]
Borrowing under credit facility	$ 13,000,000	€ 12.3