Investments & Fair Value Measurements (Schedule Of Financial Assets and Liabilities Carried At Fair Value) (Details) (USD $) | 3 Months Ended | 12 Months Ended |
Dec. 26, 2014 | Sep. 26, 2014 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | $409,115,000 | $568,472,000 |
Available-for-sale Securities, Debt Securities | 528,319,000 | 529,043,000 |
Available-for-sale Securities, Amortized Cost Basis | | 295,880,000 |
Investment Owned, at Cost | 937,911,000 | 1,095,295,000 |
Investment Owned, Unrecognized Unrealized Appreciation | 1,600,000 | 854,000 |
Investment Owned, Unrecognized Unrealized Depreciation | -505,000 | -134,000 |
Cash Cash Equivalents And Investments Total | 939,006,000 | 1,096,015,000 |
Financial assets carried at fair value | | 0 |
Contingent Consideration Classified as Equity, Fair Value Disclosure | 740,000 | |
Restricted Cash and Cash Equivalents | 2,040,000 | 2,142,000 |
Long-term investments | 318,448,000 | 296,335,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 277,507,000 | 166,075,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | -505,000 | -134,000 |
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis | 211,262,000 | 232,944,000 |
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value | 211,443,000 | 233,208,000 |
Available For Sale Securities Debt Maturities After One Through Two Years Amortized Cost | 176,989,000 | 179,177,000 |
Available For Sale Securities Debt Maturities After One Through Two Years Fair Value | 177,073,000 | 179,536,000 |
Available For Sale Securities Debt Maturities After Two Through Three Years Amortized Cost | 140,023,000 | 116,204,000 |
Available For Sale Securities Debt Maturities After Two Through Three Years Fair Value | 139,803,000 | 116,299,000 |
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis | 528,274,000 | 528,325,000 |
Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 2,266,000 | 1,727,000 |
Investments, Fair Value Disclosure | 3,513,000 | 35,445,000 |
Investments, Noncurrent, Fair Value Disclosure | 19,741,000 | 31,993,000 |
Financial assets carried at fair value | 25,520,000 | 69,165,000 |
Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 2,000,000 |
Investments, Fair Value Disclosure | 207,930,000 | 195,763,000 |
Investments, Noncurrent, Fair Value Disclosure | 298,207,000 | 263,842,000 |
Financial assets carried at fair value | 506,137,000 | 461,605,000 |
Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 0 |
Investments, Fair Value Disclosure | | 0 |
Investments, Noncurrent, Fair Value Disclosure | | 0 |
Financial assets carried at fair value | | 0 |
Contingent Consideration Classified as Equity, Fair Value Disclosure | 740,000 | |
Cash [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 406,849,000 | 564,745,000 |
Financial assets carried at fair value | | |
Cash [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets carried at fair value | | |
Cash [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets carried at fair value | | |
Cash [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Financial assets carried at fair value | | |
Money Market Funds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 2,266,000 | 1,727,000 |
Financial assets carried at fair value | | 0 |
Money Market Funds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | 2,266,000 | 1,727,000 |
Money Market Funds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | |
Money Market Funds [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | |
Commercial Paper [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 2,000,000 |
Financial assets carried at fair value | | 0 |
Commercial Paper [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | |
Commercial Paper [Member] | Level 3 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | |
U.S. Agency Securities [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Debt Securities, Amortized Cost Basis | 3,509,000 | 35,443,000 |
Available-for-sale Debt Securities Gross Unrealized Gain | 4,000 | 5,000 |
Available-for-sale Debt Securities, Gross Unrealized Loss | | 3,000 |
Available-for-sale Securities, Debt Securities | 3,513,000 | 35,445,000 |
Available-for-sale Securities, Amortized Cost Basis | 4,999,000 | 31,980,000 |
Available-for-sale Securities, Gross Unrealized Gain | 0 | 19,000 |
Available-for-sale Securities, Gross Unrealized Loss | -1,000 | -6,000 |
Available-for-sale Securities | 4,998,000 | 31,993,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 18,692,000 | 31,930,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | -41,000 | -9,000 |
U.S. Agency Securities [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 3,513,000 | 35,445,000 |
Investments, Noncurrent, Fair Value Disclosure | 4,998,000 | 31,993,000 |
Government Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 13,733,000 | |
Available-for-sale Securities, Gross Unrealized Gain | 0 | |
Available-for-sale Securities, Gross Unrealized Loss | -40,000 | |
Available-for-sale Securities | 13,693,000 | |
Government Bonds [Member] | Level 1 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Noncurrent, Fair Value Disclosure | 13,693,000 | |
Commercial Paper [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Debt Securities, Amortized Cost Basis | 8,996,000 | 21,788,000 |
Available-for-sale Debt Securities Gross Unrealized Gain | 1,000 | 0 |
Available-for-sale Debt Securities, Gross Unrealized Loss | 1,000 | 0 |
Available-for-sale Securities, Debt Securities | 8,996,000 | 21,788,000 |
Investment Owned, at Cost | 3,996,000 | 0 |
Investment Owned, Unrecognized Unrealized Appreciation | -1,000 | 0 |
Commercial Paper [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Cash and Cash Equivalents, Fair Value Disclosure | | 2,000,000 |
Investments, Fair Value Disclosure | 8,996,000 | 21,788,000 |
Corporate Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Debt Securities, Amortized Cost Basis | 88,447,000 | 56,106,000 |
Available-for-sale Debt Securities Gross Unrealized Gain | 57,000 | 81,000 |
Available-for-sale Debt Securities, Gross Unrealized Loss | 56,000 | 10,000 |
Available-for-sale Securities, Debt Securities | 88,448,000 | 56,177,000 |
Available-for-sale Securities, Amortized Cost Basis | 140,883,000 | 117,063,000 |
Available-for-sale Securities, Gross Unrealized Gain | 95,000 | 226,000 |
Available-for-sale Securities, Gross Unrealized Loss | -263,000 | -80,000 |
Available-for-sale Securities | 140,715,000 | 117,209,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 177,838,000 | 78,166,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | -319,000 | -90,000 |
Corporate Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 88,448,000 | 56,177,000 |
Investments, Noncurrent, Fair Value Disclosure | 140,715,000 | 117,209,000 |
Municipal Bonds [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Debt Securities, Amortized Cost Basis | 110,310,000 | 117,606,000 |
Available-for-sale Debt Securities Gross Unrealized Gain | 176,000 | 197,000 |
Available-for-sale Debt Securities, Gross Unrealized Loss | | 5,000 |
Available-for-sale Securities, Debt Securities | 110,486,000 | 117,798,000 |
Available-for-sale Securities, Amortized Cost Basis | 157,419,000 | 146,337,000 |
Available-for-sale Securities, Gross Unrealized Gain | 217,000 | 326,000 |
Available-for-sale Securities, Gross Unrealized Loss | -144,000 | -30,000 |
Available-for-sale Securities | 157,492,000 | 146,633,000 |
Investment Owned, at Cost | 76,981,000 | 55,979,000 |
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | -144,000 | -35,000 |
Municipal Bonds [Member] | Level 2 [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Investments, Fair Value Disclosure | 110,486,000 | 117,798,000 |
Investments, Noncurrent, Fair Value Disclosure | 157,492,000 | 146,633,000 |
Short-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Debt Securities, Amortized Cost Basis | 211,262,000 | 230,943,000 |
Available-for-sale Debt Securities Gross Unrealized Gain | 238,000 | 283,000 |
Available-for-sale Debt Securities, Gross Unrealized Loss | 57,000 | 18,000 |
Available-for-sale Securities, Debt Securities | 211,443,000 | 231,208,000 |
Other Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 500,000 | 500,000 |
Available-for-sale Securities, Gross Unrealized Gain | 1,050,000 | 0 |
Available-for-sale Securities, Gross Unrealized Loss | 0 | 0 |
Available-for-sale Securities | 1,550,000 | 500,000 |
Investments, Noncurrent, Fair Value Disclosure | 1,050,000 | |
Long-term investments | 500,000 | |
Cost Method Investment, Fair Value Measurement Adjustment | 1,100,000 | |
Long-term Investments [Member] | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | |
Available-for-sale Securities, Amortized Cost Basis | 317,534,000 | |
Available-for-sale Securities, Gross Unrealized Gain | 1,362,000 | 571,000 |
Available-for-sale Securities, Gross Unrealized Loss | -448,000 | -116,000 |
Available-for-sale Securities | 318,448,000 | 296,335,000 |
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 | 2,554,000 | 2,507,000 |
Financial liabilities carried at fair value | $2,554,000 | $2,507,000 |