Investments & Fair Value Measurements (Schedule Of Financial Assets and Liabilities Carried At Fair Value) (Details) (USD $)	6 Months Ended	12 Months Ended
Mar. 27, 2015	Sep. 26, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 513,994,000	$ 568,472,000
Available-for-sale Securities, Debt Securities	516,712,000	529,043,000
Available-for-sale Securities, Amortized Cost Basis		295,880,000
Investment Owned, at Cost	1,031,742,000us-gaap_InvestmentOwnedAtCost	1,095,295,000us-gaap_InvestmentOwnedAtCost
Investment Owned, Unrecognized Unrealized Appreciation	844,000	854,000
Investment Owned, Unrecognized Unrealized Depreciation	(130,000)	(134,000)
Cash Cash Equivalents And Investments Total	1,032,456,000	1,096,015,000
Financial assets carried at fair value		0us-gaap_AssetsFairValueDisclosure
Contingent Consideration Classified as Equity, Fair Value Disclosure	740,000
Restricted Cash and Cash Equivalents	2,156,000	2,142,000
Long-term investments	330,298,000us-gaap_LongTermInvestments	296,335,000us-gaap_LongTermInvestments
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	129,624,000	166,075,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(130,000)	(134,000)
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Amortized Cost Basis	187,963,000	232,944,000
Available-for-sale Securities, Debt Maturities, Next Twelve Months, Fair Value	188,164,000	233,208,000
Available For Sale Securities Debt Maturities After One Through Two Years Amortized Cost	207,097,000	179,177,000
Available For Sale Securities Debt Maturities After One Through Two Years Fair Value	207,445,000	179,536,000
Available For Sale Securities Debt Maturities After Two Through Three Years Amortized Cost	120,938,000	116,204,000
Available For Sale Securities Debt Maturities After Two Through Three Years Fair Value	121,103,000	116,299,000
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis	515,998,000	528,325,000
Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	15,438,000	1,727,000
Investments, Fair Value Disclosure	2,006,000	35,445,000
Investments, Noncurrent, Fair Value Disclosure	26,317,000	31,993,000
Financial assets carried at fair value	43,761,000	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	186,158,000	195,763,000
Investments, Noncurrent, Fair Value Disclosure	303,281,000	263,842,000
Financial assets carried at fair value	489,439,000	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	498,556,000	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	15,438,000	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	15,438,000	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	1,999,000	35,443,000
Available-for-sale Debt Securities Gross Unrealized Gain	7,000	5,000
Available-for-sale Debt Securities, Gross Unrealized Loss		3,000
Available-for-sale Securities, Debt Securities	2,006,000	35,445,000
Available-for-sale Securities, Amortized Cost Basis	5,000,000	31,980,000
Available-for-sale Securities, Gross Unrealized Gain	6,000	19,000
Available-for-sale Securities, Gross Unrealized Loss	0	(6,000)
Available-for-sale Securities	5,006,000	31,993,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	17,758,000	31,930,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(33,000)	(9,000)
U.S. Agency Securities [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure	2,006,000	35,445,000
Investments, Noncurrent, Fair Value Disclosure	5,006,000	31,993,000
Government Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Securities, Amortized Cost Basis	20,290,000
Available-for-sale Securities, Gross Unrealized Gain	4,000
Available-for-sale Securities, Gross Unrealized Loss	(33,000)
Available-for-sale Securities	20,261,000
Government Bonds [Member] \| Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Noncurrent, Fair Value Disclosure	20,261,000
Commercial Paper [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	3,999,000	21,788,000
Available-for-sale Debt Securities Gross Unrealized Gain	0	0
Available-for-sale Debt Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities, Debt Securities	3,999,000	21,788,000
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	3,999,000	21,788,000
Corporate Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	79,485,000	56,106,000
Available-for-sale Debt Securities Gross Unrealized Gain	86,000	81,000
Available-for-sale Debt Securities, Gross Unrealized Loss	15,000	10,000
Available-for-sale Securities, Debt Securities	79,556,000	56,177,000
Available-for-sale Securities, Amortized Cost Basis	144,666,000	117,063,000
Available-for-sale Securities, Gross Unrealized Gain	376,000	226,000
Available-for-sale Securities, Gross Unrealized Loss	(22,000)	(80,000)
Available-for-sale Securities	145,020,000	117,209,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	64,387,000	78,166,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(37,000)	(90,000)
Corporate Bonds [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure	79,556,000	56,177,000
Investments, Noncurrent, Fair Value Disclosure	145,020,000	117,209,000
Municipal Bonds [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Available-for-sale Debt Securities, Amortized Cost Basis	102,480,000	117,606,000
Available-for-sale Debt Securities Gross Unrealized Gain	129,000	197,000
Available-for-sale Debt Securities, Gross Unrealized Loss		5,000
Available-for-sale Securities, Debt Securities	102,603,000	117,798,000
Available-for-sale Securities, Amortized Cost Basis	158,079,000	146,337,000
Available-for-sale Securities, Gross Unrealized Gain	236,000	326,000
Available-for-sale Securities, Gross Unrealized Loss	(54,000)	(30,000)
Available-for-sale Securities	158,261,000	146,633,000
Investment Owned, at Cost	47,479,000	55,979,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss	(60,000)	(35,000)
Municipal Bonds [Member] \| Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Investments, Fair Value Disclosure	102,603,000	117,798,000
Investments, Noncurrent, Fair Value Disclosure	158,261,000	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	187,963,000	230,943,000
Available-for-sale Debt Securities Gross Unrealized Gain	222,000	283,000
Available-for-sale Debt Securities, Gross Unrealized Loss	21,000	18,000
Available-for-sale Securities, Debt Securities	188,164,000	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	1,750,000	500,000
Available-for-sale Securities, Gross Unrealized Gain	0	0
Available-for-sale Securities, Gross Unrealized Loss	0	0
Available-for-sale Securities	1,750,000	500,000
Investments, Noncurrent, Fair Value Disclosure	1,050,000
Long-term investments	700,000
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	329,785,000
Available-for-sale Securities, Gross Unrealized Gain	622,000	571,000
Available-for-sale Securities, Gross Unrealized Loss	(109,000)	(116,000)
Available-for-sale Securities	330,298,000	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	2,560,000	2,507,000
Financial liabilities carried at fair value	$ 2,560,000	$ 2,507,000

Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss

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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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This item represents the fair value of debt securities 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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No definition available.

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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 two year and through three years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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This item represents the fair value of debt securities which are expected to mature after two year and through three years from the balance sheet date and which are categorized neither as held-to-maturity nor trading securities.

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No definition available.

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Business Combination, Contingent Consideration, Liability, Fair Value Disclosure

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Total Cash, Cash Equivalents And Investments

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Cost Method Investment, Fair Value Measurement Adjustment

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Investments, Noncurrent, 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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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.

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Amount of unrealized gain before deducting unrealized loss on investments in debt securities classified as available-for-sale securities.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale debt securities.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the cost of debt and equity 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.

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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.

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Amount of available-for-sale debt securities at cost, net of adjustments, which include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing in the next fiscal year following the latest fiscal year.

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Amount of debt securities categorized neither as held-to-maturity nor trading.

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Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

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Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash

-URI http://asc.fasb.org/extlink&oid=6506951

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Cash Equivalents

-URI http://asc.fasb.org/extlink&oid=6507016

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- Definition

Cost of the investment.

+ References

No definition available.

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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=6955306&loc=SL6090603-123010

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- Definition

+ References

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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 Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594

Reference 2: 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 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=28360136&loc=d3e22054-111558

Reference 4: 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

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-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

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- Definition

Fair value of financial and nonfinancial obligations.

+ References

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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

+ 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 SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 1

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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 210.5-02.1)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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