Short-Term Investments (Details) - USD ($)	12 Months Ended
Oct. 03, 2020	Sep. 28, 2019	Sep. 29, 2018
Debt Securities, Available-for-sale [Abstract]
Cash and cash equivalents: cost basis	$ 440,258,000	$ 305,833,000
Cash Equivalent, Unrealized Gains	0	0
Cash Equivalent, Unrealized Losses	0	0
Cash and cash equivalents	440,258,000	305,833,000	$ 310,495,000
Available-for-sale securities, fair value	35,346,000	120,000
Available-for-sale Securities, Debt Maturities [Abstract]
Due in less than 1 year, amortized cost	35,311,000	120,000
Due in less than 1 year, estimated fair value	35,346,000	120,000
Proceeds from sale of available-for-sale securities	5,000
Realized gross gains from sale of available-for-sale securities		0
U.S. Treasury and agency obligations
Debt Securities, Available-for-sale [Abstract]
Available-for-sale securities: cost basis	35,311,000	120,000
Available-for-sale securities: unrealized gains	36,000	0
Available-for-sale securities: unrealized losses	(1,000)	0
Available-for-sale securities, fair value	35,346,000	120,000
U.S. Treasury and agency obligations \| Short-term investments
Debt Securities, Available-for-sale [Abstract]
Available-for-sale securities: cost basis	35,311,000	120,000
Available-for-sale securities: unrealized gains	36,000	0
Available-for-sale securities: unrealized losses	(1,000)	0
Debt securities, available-for-sale	35,346,000	120,000
Corporate notes and obligations
Debt Securities, Available-for-sale [Abstract]
Debt Securities, available-for-sale, accumulated gross unrealized gain (loss), before tax	$ (100,000)	$ 0

Cash, Cash Equivalent and Restricted Cash, Cost Basis

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Cash Equivalent, Unrealized Losses

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), maturing in next fiscal year following latest fiscal year. Excludes interim and annual periods when interim period is reported on rolling approach, from latest statement of financial position date.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Amount 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. Excludes cash and cash equivalents within disposal group and discontinued operation.

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Amount, before tax, of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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