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Marketable Securities (Amortized Cost and Fair Value of Marketable Securities) (Details) - USD ($) $ in Thousands | Jun. 29, 2019 | Sep. 30, 2018
--- | --- | ---
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | $ 54,561 | $ 56,364
Gross unrealized gains | 124 | 0
Gross unrealized losses | (59) | (413)
Fair value | 54,626 | 55,951
Certificates of deposit |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost |  | 220
Gross unrealized gains |  | 0
Gross unrealized losses |  | (1)
Fair value |  | 219
Commercial paper |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 4,474 |
Gross unrealized gains | 1 |
Gross unrealized losses | 0 |
Fair value | 4,475 |
Corporate notes/bonds |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost | 50,087 | 55,140
Gross unrealized gains | 123 | 0
Gross unrealized losses | (59) | (403)
Fair value | $ 50,151 | 54,737
U.S. government agency securities |  |
Debt Securities, Available-for-sale [Line Items] |  |
Amortized cost |  | 1,004
Gross unrealized gains |  | 0
Gross unrealized losses |  | (9)
Fair value |  | $ 995

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- Definition Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563 + Details
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- Definition Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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