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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
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

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- Definition

This item represents debt securities, at cost, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments, as defined), and fair value hedge accounting adjustments, if any, which are expected to mature after one year and through Two years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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Business Combination, Contingent Consideration, Liability, Fair Value Disclosure

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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