Fair Value Measurements (Schedule Of Financial Assets and Liabilities Carried At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 27, 2013		Sep. 27, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	$ 481,154		$ 480,175
Financial liabilities carried at fair value	2,316	[1]	2,242
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	63,176		78,501
Financial liabilities carried at fair value	2,316	[1]	2,242
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	417,978		401,674
Financial liabilities carried at fair value	0	[1]	0
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0		0
Financial liabilities carried at fair value	0	[1]	0
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	2,813	[2]	16,193	[2]
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	2,813	[2]	16,193	[2]
Money Market Funds [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2]	0	[2]
Money Market Funds [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2]	0	[2]
Investments Held In Supplemental Retirement Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	2,316	[3]	2,242	[3]
Financial liabilities carried at fair value			2,242	[1]
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	2,316	[3]	2,242	[3]
Financial liabilities carried at fair value			2,242	[1]
Investments Held In Supplemental Retirement Plan [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[3]	0	[3]
Financial liabilities carried at fair value			0	[1]
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	0	[3]	0	[3]
Financial liabilities carried at fair value			0	[1]
U.S. Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	58,047	[2],[4],[5]	60,066	[4],[5]
U.S. Agency Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	58,047	[2],[4],[5]	60,066	[4],[5]
U.S. Agency Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2],[4],[5]	0	[4],[5]
U.S. Agency Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2],[4],[5]	0	[4],[5]
Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	20,618	[2],[5]	10,991	[2],[5]
Commercial Paper [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2],[5]	0	[2],[5]
Commercial Paper [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	20,618	[2],[5]	10,991	[2],[5]
Commercial Paper [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[2],[5]	0	[2],[5]
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	123,953	[4],[5]	134,238	[2],[5]
Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[4],[5]	0	[2],[5]
Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	123,953	[4],[5]	134,238	[2],[5]
Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[4],[5]	0	[2],[5]
Municipal Debt Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	273,407	[4],[5]	256,445	[2],[4],[5]
Municipal Debt Securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[4],[5]	0	[2],[4],[5]
Municipal Debt Securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	273,407	[4],[5]	256,445	[2],[4],[5]
Municipal Debt Securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	$ 0	[4],[5]	$ 0	[2],[4],[5]

[1] These liabilities are included within accrued liabilities and within other non-current liabilities.

[2] These assets are included within cash and cash equivalents.

[3] These assets are included within prepaid expenses and other current assets and within other non-current assets.

[4] These assets are included within long-term investments.

[5] These assets are included within short-term investments.