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Summary of Financial Assets Measured at Fair Value on Recurring Basis (Detail) (USD $)
In Millions, unless otherwise specified |
Apr. 28, 2012
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Jul. 30, 2011
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial assets carried at fair value | $ 246.6 | $ 191.2 | ||||||
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Municipal bonds | Level 1
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial assets carried at fair value | 237.0 | [1] | 179.2 | [1] | ||||
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Auction rate securities | Level 3
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| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||||||||
| Financial assets carried at fair value | $ 9.6 | [2] | $ 12.0 | [2] | ||||
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