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Composition Of Certain Financial Statement Captions (Schedule Of Investment Portfolio Recorded As Cash Equivalents, Short-Term Investments, And Long-Term Investments) (Details) (USD $) In Thousands | Sep. 30, 2011 | Sep. 24, 2010
--- | --- | ---
Investment Holdings [Line Items] |  |
Cost | $ 820,030 | $ 879,935
Unrealized Gain | 1,632 | 2,621
Unrealized Loss | (546) | (29)
Estimated Fair Value | 821,116 | 882,527
Corporate Bonds [Member] |  |
Investment Holdings [Line Items] |  |
Cost | 177,129 | 29,238
Unrealized Gain | 316 | 420
Unrealized Loss | (487) |
Estimated Fair Value | 176,958 | 29,658
Commercial Paper [Member] |  |
Investment Holdings [Line Items] |  |
Cost |  | 29,983
Estimated Fair Value |  | 29,983
Municipal Debt Securities [Member] |  |
Investment Holdings [Line Items] |  |
Cost | 471,005 | 318,825
Unrealized Gain | 1,251 | 1,781
Unrealized Loss | (55) | (25)
Estimated Fair Value | 472,201 | 320,581
U.S. Agency Securities [Member] |  |
Investment Holdings [Line Items] |  |
Cost | 29,858 | 107,512
Unrealized Gain | 65 | 390
Unrealized Loss | (4) | (4)
Estimated Fair Value | 29,919 | 107,898
U.S. Government Bonds [Member] |  |
Investment Holdings [Line Items] |  |
Cost |  | 39,949
Unrealized Gain |  | 30
Estimated Fair Value |  | 39,979
Money Market Funds [Member] |  |
Investment Holdings [Line Items] |  |
Cost | 142,038 | 354,428
Estimated Fair Value | $ 142,038 | $ 354,428

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