Accumulated Other Comprehensive Loss (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Nov. 30, 2014	Nov. 30, 2013	Nov. 30, 2014	Nov. 30, 2013	Aug. 31, 2014
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	$ (37.9)	$ (38.6)	$ (29.3)	$ (42.5)
Other comprehensive income (loss) before reclassifications	(14.9)	8.4	(23.6)	12.1
Amounts reclassified from AOCL		0.3	0.1	0.5
Other comprehensive (loss) income, net of tax	(14.9)	8.7	(23.5)	12.6
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(52.8)	(29.9)	(52.8)	(29.9)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(0.3)	(2.6)	8.7	(5.4)
Other comprehensive income (loss) before reclassifications	(14.8)	9.0	(23.8)	11.8
Other comprehensive (loss) income, net of tax	(14.8)	9.0	(23.8)	11.8
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(15.1)	6.4	(15.1)	6.4
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance		(33.6)	(35.4)	(33.8)	(35.3)
Amounts reclassified from AOCL		0.3	0.1	0.5
Other comprehensive (loss) income, net of tax		0.3	0.1	0.5
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	(35.3)	(33.3)	(35.3)	(33.3)	(35.3)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning Balance	(2.3)	(2.4)	(2.6)	(3.3)
Other comprehensive income (loss) before reclassifications	(0.1)	(0.6)	0.2	0.3
Other comprehensive (loss) income, net of tax	(0.1)	(0.6)	0.2	0.3
Accumulated Other Comprehensive Income (Loss), Net of Tax, Ending Balance	$ (2.4)	$ (3.0)	$ (2.4)	$ (3.0)