v2.4.0.6
Fair Value Measurements - Additional Information (Detail) (USD $)
In Millions, unless otherwise specified
Apr. 28, 2012
Jul. 30, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Amount by which fair value of available-for-sale securities is lower than cost basis $ 1.0 $ 2.4