Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2013
Cash Flow Supplemental Disclosures [Line Items]
Interest paid, net of amount capitalized	$ 36,190	$ 24,199	$ 22,614
Income taxes paid, net of refunds	$ 67,825	$ 81,997	$ 64,260