Fair Value Measurements (Schedule Of Financial Assets Carried At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 29, 2013		Sep. 28, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	$ 2,144		$ 2,140
Financial assets carried at fair value	454,272		690,425
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	2,144		2,140
Financial assets carried at fair value	58,650		44,242
Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	0		0
Financial assets carried at fair value	395,622		646,183
Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	0		0
Financial assets carried at fair value	0		0
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	156,756	[1]	220,236	[1]
Corporate Bonds [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1]
Corporate Bonds [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	156,756	[1]	220,236	[1]
Corporate Bonds [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1]
Municipal debt securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	231,886	[1]	401,648	[1],[2]
Municipal debt securities [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1],[2]
Municipal debt securities [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	231,886	[1]	401,648	[1],[2]
Municipal debt securities [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1],[2]
U.S. Agency Securities [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	53,739	[1]	25,012	[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	53,739	[1]	25,012	[1]
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	[1]	0	[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	0	[1]	0	[1]
Money Market Funds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	2,767	[2]	17,090	[2]
Money Market Funds [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	2,767	[2]	17,090	[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]
Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	6,980	[1]	24,299	[1],[2]
Commercial Paper [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1],[2]
Commercial Paper [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	6,980	[1]	24,299	[1],[2]
Commercial Paper [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial assets carried at fair value	0	[1]	0	[1],[2]
Investments Held In Supplemental Retirement Plan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	2,144	[3],[4]	2,140
Financial assets carried at fair value			2,140	[4]
Investments Held In Supplemental Retirement Plan [Member] | Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	2,144	[3],[4]	2,140	[3]
Financial assets carried at fair value			2,140	[4]
Investments Held In Supplemental Retirement Plan [Member] | Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	0	[3],[4]	0	[3]
Financial assets carried at fair value			0	[4]
Investments Held In Supplemental Retirement Plan [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Financial liabilities carried at fair value	0	[3],[4]	0	[3]
Financial assets carried at fair value			$ 0	[4]

[1] These assets are included within short-term investments and within long-term investments.

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

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

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