Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Aug. 31, 2015	May. 31, 2015
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total cash collateral	$ 2,711,000
Impact to fair value of derivative assets and liabilities as a result of recognition on a net basis	(310,000)	$ 500,000
Losses in accumulated other comprehensive income expected to be reclassified into net earnings	(12,131,000)
Losses in accumulated other comprehensive income expected to be reclassified into net earnings, tax	$ 7,029,000