v2.4.0.6
Summary of Short-Term and Non-current Investments by Maturity Date (Detail) (USD $)
In Millions, unless otherwise specified
Apr. 28, 2012
Jul. 30, 2011
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year $ 73.0 $ 54.1
Available-for-sale investments maturities 1 to 3 years 129.6 102.7
Available-for-sale investments maturities over 3 years 50.7 35.8
Available-for-sale investments, Total 253.3 192.6
Available-for-sale investments - short-term
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 69.0 54.1
Available-for-sale investments maturities 1 to 3 years 129.6 0
Available-for-sale investments maturities over 3 years 48.0 0
Available-for-sale investments, Total 246.6 54.1
Available-for-sale investments - short-term | Municipal bonds
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 66.3 52.7
Available-for-sale investments maturities 1 to 3 years 129.6 0
Available-for-sale investments maturities over 3 years 41.1 0
Available-for-sale investments, Total 237.0 52.7
Available-for-sale investments - short-term | Auction rate securities
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 0 0
Available-for-sale investments maturities 1 to 3 years 0 0
Available-for-sale investments maturities over 3 years 6.9 0
Available-for-sale investments, Total 6.9 0
Available-for-sale investments - short-term | Restricted cash
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 2.7 1.4
Available-for-sale investments maturities 1 to 3 years 0 0
Available-for-sale investments maturities over 3 years 0 0
Available-for-sale investments, Total 2.7 1.4
Available-for-sale investments - non-current
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 0 0
Available-for-sale investments maturities 1 to 3 years 0 102.7
Available-for-sale investments maturities over 3 years 2.7 35.8
Available-for-sale investments, Total 2.7 138.5
Available-for-sale investments - non-current | Municipal bonds
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 0 0
Available-for-sale investments maturities 1 to 3 years 0 102.7
Available-for-sale investments maturities over 3 years 0 23.8
Available-for-sale investments, Total 0 126.5
Available-for-sale investments - non-current | Auction rate securities
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 0 0
Available-for-sale investments maturities 1 to 3 years 0 0
Available-for-sale investments maturities over 3 years 2.7 12.0
Available-for-sale investments, Total 2.7 12.0
Other non-current investments
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 4.0 0
Available-for-sale investments maturities 1 to 3 years 0 0
Available-for-sale investments maturities over 3 years 0 0
Available-for-sale investments, Total 4.0 0
Total non-current investments
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 4.0 0
Available-for-sale investments maturities 1 to 3 years 0 102.7
Available-for-sale investments maturities over 3 years 2.7 35.8
Available-for-sale investments, Total $ 6.7 $ 138.5