Summary of Changes in Equity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Oct. 29, 2011	Oct. 30, 2010
Stockholders Equity Note [Line Items]
Balance at beginning of period	$ 1,158.0	$ 1,014.7	[1]
Comprehensive income:
Net income	47.5	48.0	[1]
Foreign currency translation adjustment	(0.2)
Net unrealized loss on available-for-sale investments	(0.2)
Total comprehensive income	47.1	48.0	[1]
Change in non-controlling interest		(0.1)	[1]
Purchases of common stock	(28.7)
Shares issued and equity grants made pursuant to stock-based compensation plans	9.6	5.5	[1]
Balance at end of period	$ 1,186.0	$ 1,068.1	[1]

[1] Includes amounts attributable to a non-controlling interest of $1.4 million as of July 31, 2010 and $1.5 million as of October 30, 2010. The Company sold its interest in its majority-owned investment during the fourth quarter of Fiscal 2011, thereby eliminating the non-controlling interest.