Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Aug. 31, 2015	Aug. 31, 2014	May. 31, 2015
Income Tax [Line Items]
Effective income tax rate	29.40%	29.20%
Federal statutory rate	35.00%
Undistributed foreign earnings	$ 400,800,000		$ 419,100,000
Deferred income tax liability	101,600,000		$ 108,500,000
Provision for deferred income taxes	$ 0