Compensation Expense Recognized on Awards (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 31, 2013	Oct. 31, 2012
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 2.7	$ 2.6
Income tax effect	(0.9)	(0.8)
Total share-based compensation included in net (loss) income	1.8	1.8
Performance-based EPS related condition compensation expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.5	1.1
Performance-based TSR related condition compensation expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	0.6	0.7
Total performance-based stock compensation expense
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	1.1	1.8
Time-based stock options and restricted stock
Compensation Related Costs Share Based Payments Disclosure [Line Items]
Share-based compensation expense before tax	$ 1.6	$ 0.8