Derivative Instruments and Hedging Activities (Details 2) (Cash flow hedges, USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Nov. 30, 2011	Nov. 30, 2012	Nov. 30, 2011
Cash flow hedges
Impact of the interest rate swap and interest cap agreement on the condensed consolidated statement of income
Amount of unrealized pre-tax loss recorded in accumulated comprehensive income (loss)	$ (0.2)	$ (0.4)	$ (2.7)