Derivative Instruments and Hedging Activities - Additional Information (Detail) - USD ($)	12 Months Ended
	May. 31, 2015	May. 31, 2014
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Total cash collateral	$ 2,248,000
Impact to fair value of derivative assets and liabilities as a result of recognition on a net basis	500,000	$ 730,000
Losses in accumulated other comprehensive income expected to be reclassified into net earnings	(12,619,000)
Losses in accumulated other comprehensive income expected to be reclassified into net earnings, tax	$ 7,518,000