Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013
Equity [Abstract]
Amortization of interest rate locks	$ (783)	$ (783)	$ (1,565)	$ (1,565)
Tax benefit	295	295	589	589
Amortization of interest rate locks, net of tax	$ (488)	$ (488)	$ (976)	$ (976)