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Summary of Changes in Equity (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended 9 Months Ended
Apr. 28, 2012
Apr. 30, 2011
Apr. 28, 2012
Apr. 30, 2011
Stockholders Equity Note [Line Items]        
Balance at beginning of period     $ 1,158.0 $ 1,014.7 [1]
Comprehensive income:        
Net income 49.4 51.8 160.6 142.3 [1]
Foreign currency translation adjustment     0.1 0 [1]
Net change in unrealized gains (losses) on available-for-sale investments     1.4 0.9 [1]
Total comprehensive income     162.1 143.2 [1]
Other, including change in non-controlling interest in Fiscal 2011     2.7 (0.2) [1]
Purchases of common stock     (37.2) (47.4) [1]
Shares issued and equity grants made pursuant to stock-based compensation plans     39.7 31.8 [1]
Balance at end of period $ 1,325.3 $ 1,142.1 [1] $ 1,325.3 $ 1,142.1 [1]
[1] Includes amounts attributable to a non-controlling interest of $1.4 million as of July 31, 2010 and $1.6 million as of April 30, 2011. The Company sold its interest in its majority-owned investment during the fourth quarter of Fiscal 2011, thereby eliminating the non-controlling interest.