Total Unrecognized Compensation and Weighted-average Years Expected to be Recognized (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 29, 2011 Year
Unrecognized Share Based Compensation Expense [Line Items]
Total unrecognized compensation cost	$ 33.4
Weighted-average recognition period for unrecognized compensation cost (years)	3.0
Service-based Restricted Equity Awards
Unrecognized Share Based Compensation Expense [Line Items]
Total unrecognized compensation cost	11.0
Weighted-average recognition period for unrecognized compensation cost (years)	3.5
Performance-based Restricted Equity Awards
Unrecognized Share Based Compensation Expense [Line Items]
Total unrecognized compensation cost	15.8
Weighted-average recognition period for unrecognized compensation cost (years)	2.1
Market-based Restricted Equity Awards
Unrecognized Share Based Compensation Expense [Line Items]
Total unrecognized compensation cost	$ 3.3
Weighted-average recognition period for unrecognized compensation cost (years)	2.0