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, 2013		Nov. 30, 2012		Nov. 30, 2013		Nov. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of interest rate locks	$ (783)				$ (1,565)
Tax benefit	295		300		589		600
Amortization of interest rate locks, net of tax	$ (488)	[1]	$ (488)	[1]	$ (976)	[1]	$ (976)	[1]

[1] Net of $0.3 million of tax benefit for the three months ended November 30, 2013 and 2012. Net of $0.6 million of tax benefit for the six months ended November 30, 2013 and 2012.