Accumulated Other Comprehensive (Loss) Income - Reclassifications Out of Accumulated Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Feb. 28, 2015	Feb. 28, 2014	Feb. 28, 2015	Feb. 28, 2014
Equity [Abstract]
Amortization of interest rate locks	$ (783)	$ (783)	$ (2,348)	$ (2,348)
Tax benefit	295	295	884	884
Amortization of interest rate locks, net of tax	$ (488)	$ (488)	$ (1,464)	$ (1,464)