Fair Value Measurements (Schedule Of Financial Assets Carried At Fair Value) (Details) (USD $)
| Sep. 30, 2011 | Sep. 24, 2010 |
|---|
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | $ 823,007,000 | | $ 884,727,000 | |
| Notional amount of derivative | 4,700,000 | | | |
Commercial Paper [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | 29,983,000 | [1] |
Commercial Paper [Member] | Level 2 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | 29,983,000 | [1] |
Commercial Paper [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
Corporate Bonds [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 176,958,000 | [2] | 29,658,000 | [1] |
Corporate Bonds [Member] | Level 2 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 176,958,000 | [2] | 29,658,000 | [1] |
Corporate Bonds [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
Municipal Debt Securities [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 472,201,000 | [2] | 320,581,000 | [1] |
Municipal Debt Securities [Member] | Level 2 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 472,201,000 | [2] | 320,581,000 | [1] |
Municipal Debt Securities [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
U.S. Agency Securities [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 29,919,000 | [2],[3] | 107,898,000 | [1] |
U.S. Agency Securities [Member] | Level 1 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 29,919,000 | [2],[3] | 107,898,000 | [1] |
U.S. Agency Securities [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
U.S. Government Bonds [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | 39,979,000 | [1] |
U.S. Government Bonds [Member] | Level 1 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | 39,979,000 | [1] |
U.S. Government Bonds [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
Investments Held In Supplemental Retirement Plan [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 1,891,000 | [4] | 2,200,000 | [4] |
Investments Held In Supplemental Retirement Plan [Member] | Level 1 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 1,891,000 | [4] | 2,200,000 | [4] |
Investments Held In Supplemental Retirement Plan [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [4] |
Money Market Funds [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 142,038,000 | [3] | 354,428,000 | [1] |
Money Market Funds [Member] | Level 1 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 142,038,000 | [3] | 354,428,000 | [1] |
Money Market Funds [Member] | Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | [1] |
Level 1 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 173,848,000 | | 504,505,000 | |
Level 2 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | 649,159,000 | | 380,222,000 | |
Level 3 [Member] | | | | |
| Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | |
| Financial assets carried at fair value | | | | |
|
|