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Investments & Fair Value Measurements (Schedule Of Financial Assets and Liabilities Carried At Fair Value) (Details) - USD ($) $ in Thousands | Jan. 01, 2016 | Sep. 25, 2015
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Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | $ 467,099 | $ 531,926
Available-for-sale Debt Securities, Amortized Cost Basis | 452,382 | 476,407
Available-for-sale Securities, Debt Securities | 451,555 | 476,419
Available-for-sale Securities | 266,904 | 321,015
Investment Owned, at Cost | 873,532 | 991,104
Investment Owned, Unrecognized Unrealized Appreciation | 572 | 1,218
Investment Owned, Unrecognized Unrealized Depreciation | (957) | (480)
Cash Cash Equivalents And Investments Total | 873,147 | 991,842
Financial assets carried at fair value |  | 531,926
Contingent Consideration Classified as Equity, Fair Value Disclosure | 95 | 95
Restricted Cash and Cash Equivalents | 4,331 | 2,936
Long-term investments | 266,904 | 321,015
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 299,034 | 202,515
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (957) | (480)
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis | 187,978 | 158,957
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value | 187,904 | 159,090
Available For Sale Securities Debt Maturities After One Through Two Years Amortized Cost | 133,489 | 173,571
Available For Sale Securities Debt Maturities After One Through Two Years Fair Value | 133,256 | 173,577
Available For Sale Securities Debt Maturities After Two Through Three Years Amortized Cost | 130,915 | 143,879
Available For Sale Securities Debt Maturities After Two Through Three Years Fair Value | 130,395 | 143,752
Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 49,126 | 19,014
Investments, Fair Value Disclosure |  | 2,001
Investments, Noncurrent, Fair Value Disclosure | 31,742 | 33,233
Financial assets carried at fair value | 80,868 | 54,248
Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 1,176
Investments, Fair Value Disclosure | 139,144 | 136,900
Investments, Noncurrent, Fair Value Disclosure | 232,350 | 284,821
Financial assets carried at fair value | 371,494 | 422,897
Level 3 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Contingent Consideration Classified as Equity, Fair Value Disclosure | 95 | 95
Cash [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 417,973 | 511,736
Money Market Funds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 49,126 | 19,014
Money Market Funds [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure | 49,126 | 19,014
Certificates of Deposit [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 8,500 |
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 0 |
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 |
Available-for-sale Securities | 8,500 |
Certificates of Deposit [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Noncurrent, Fair Value Disclosure | 8,500 |
U.S. Agency Securities [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Debt Securities, Amortized Cost Basis |  | 2,000
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax |  | 1
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax |  | 0
Available-for-sale Securities, Debt Securities |  | 2,001
Available-for-sale Securities, Amortized Cost Basis | 999 | 1,999
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 1 | 1
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Available-for-sale Securities | 1,000 | 2,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 29,302 | 19,005
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (186) | (17)
U.S. Agency Securities [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Fair Value Disclosure |  | 2,001
Investments, Noncurrent, Fair Value Disclosure | 1,000 | 2,000
Government Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 30,486 | 30,505
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 1 | 19
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (186) | (17)
Available-for-sale Securities | 30,301 | 30,507
Government Bonds [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Noncurrent, Fair Value Disclosure | 30,301 | 30,507
Commercial Paper [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Debt Securities, Amortized Cost Basis | 13,843 | 6,478
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax | 0 | 0
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax | (11) | 0
Available-for-sale Securities, Debt Securities | 13,832 | 6,478
Investment Owned, at Cost | 13,832 | 0
Investment Owned, Unrecognized Unrealized Appreciation | 11 | 0
Commercial Paper [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Fair Value Disclosure | 13,832 | 6,478
Corporate Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Cash and Cash Equivalents, Fair Value Disclosure |  | 1,176
Available-for-sale Debt Securities, Amortized Cost Basis | 83,258 | 86,543
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax | 9 | 46
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax | (103) | (11)
Available-for-sale Securities, Debt Securities | 83,164 | 86,578
Available-for-sale Securities, Amortized Cost Basis | 149,384 | 167,394
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 40 | 138
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (563) | (392)
Available-for-sale Securities | 148,861 | 167,140
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value | 195,014 | 148,034
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (666) | (403)
Corporate Bonds [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Fair Value Disclosure |  | 1,176
Corporate Bonds [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Fair Value Disclosure | 83,164 | 86,578
Investments, Noncurrent, Fair Value Disclosure | 148,861 | 167,140
Municipal Bonds [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Debt Securities, Amortized Cost Basis | 42,116 | 43,746
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax | 39 | 98
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax | (7) | 0
Available-for-sale Securities, Debt Securities | 42,148 | 43,844
Available-for-sale Securities, Amortized Cost Basis | 75,035 | 117,552
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 41 | 189
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (87) | (60)
Available-for-sale Securities | 74,989 | 117,681
Investment Owned, at Cost | 60,886 | 35,476
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss | (94) | (60)
Municipal Bonds [Member] | Level 2 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Fair Value Disclosure | 42,148 | 43,844
Investments, Noncurrent, Fair Value Disclosure | 74,989 | 117,681
Short-term Investments [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Debt Securities, Amortized Cost Basis | 139,217 | 138,767
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax | 48 | 145
Available-for-sale Debt Securities, Accumulated Gross Unrealized Loss, before Tax | (121) | (11)
Available-for-sale Securities, Debt Securities | 139,144 | 138,901
Other Long-term Investments [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 2,812 | 2,961
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 441 | 726
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | 0 | 0
Available-for-sale Securities | 3,253 | 3,687
Investments, Noncurrent, Fair Value Disclosure | 300 | 500
Cost Method Investment, Fair Value Measurement Adjustment | 400 | 700
Other Long-term Investments [Member] | Level 1 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Investments, Noncurrent, Fair Value Disclosure | 441 | 726
Long-term Investments [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Available-for-sale Securities, Amortized Cost Basis | 267,216 | 320,411
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax | 524 | 1,073
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax | (836) | (469)
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 | 2,579 | 2,498
Financial liabilities carried at fair value | 2,579 | 2,498
Cost Method Investment 1 [Member] | Other Long-term Investments [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term investments | 2,000 | 2,000
Cost Method Investment 2 [Member] | Other Long-term Investments [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Long-term investments | $ 500 | $ 500

X
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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 + Details
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- Definition This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (aa) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.2) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27337-111563 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 6 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27290-111563 + Details
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- Definition Cost of the investment. + References No definition available. + Details
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- Definition This element represents the excess of the cost (face amount, notional amount) of an investment (security, contract) over its fair value which deficiency has not been recognized in earnings of the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=50485924&loc=SL6090603-123010 + Details
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- Definition This element represents the excess of the cost (face amount, notional amount) of an investment (security, contract) over its fair value which deficiency has not been recognized in earnings of the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 22 -URI http://asc.fasb.org/extlink&oid=50485924&loc=SL6090603-123010 + Details
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- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 + Details
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- Definition Fair value of financial and nonfinancial obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 + Details
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- Definition The total amount of investments that are intended to be held for an extended period of time (longer than one operating cycle). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.12) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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