v2.4.0.6
Summary of Short-Term and Non-current Investments by Maturity Date (Detail) (USD $)
In Millions, unless otherwise specified
Jul. 28, 2012
Jul. 30, 2011
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year $ 1.9 $ 54.1
Available-for-sale investments maturities 1 to 3 years   102.7
Available-for-sale investments maturities over 3 years 2.7 35.8
Available-for-sale investments, Total 4.6 192.6
Available-for-sale investments - short-term
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 1.4 54.1
Available-for-sale investments, Total 1.4 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   52.7
Available-for-sale investments, Total   52.7
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 1.4 1.4
Available-for-sale investments, Total 1.4 1.4
Available-for-sale investments - non-current
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities 1 to 3 years   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 1 to 3 years   102.7
Available-for-sale investments maturities over 3 years   23.8
Available-for-sale investments, Total   126.5
Available-for-sale investments - non-current | Auction rate securities
   
Schedule of Available-for-sale Securities [Line Items]    
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 0.5  
Available-for-sale investments, Total 0.5  
Total non-current investments
   
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale investments maturities less than 1 year 0.5  
Available-for-sale investments maturities 1 to 3 years   102.7
Available-for-sale investments maturities over 3 years 2.7 35.8
Available-for-sale investments, Total $ 3.2 $ 138.5