Comprehensive Income - Additional Information (Detail) (USD $)	12 Months Ended
	May 31, 2014	May 31, 2013	May 31, 2012
Other Comprehensive Income (Loss) [Line Items]
Net loss reclassified from AOCI for cash flow hedges	$ (5,965,000)	$ (1,604,000)	$ (1,245,000)
Net loss reclassified from AOCI for cash flow hedges, tax	3,536,000	827,000	794,000
Losses in accumulated other comprehensive income expected to be reclassified into net earnings	(1,287,000)
Losses in accumulated other comprehensive income expected to be reclassified into net earnings, tax	$ 763,000