Marketable Securities (Amortized Cost and Fair Value of Marketable Securities) (Details) - USD ($) $ in Thousands	Dec. 29, 2018	Sep. 30, 2018
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	$ 56,050	$ 56,364
Gross unrealized gains	6	0
Gross unrealized losses	(405)	(413)
Fair value	55,651	55,951
Certificates of deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	221	220
Gross unrealized gains	0	0
Gross unrealized losses	(1)	(1)
Fair value	220	219
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,961
Gross unrealized gains	0
Gross unrealized losses	(5)
Fair value	1,956
Corporate notes/bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	52,868	55,140
Gross unrealized gains	6	0
Gross unrealized losses	(394)	(403)
Fair value	52,480	54,737
U.S. government agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized cost	1,000	1,004
Gross unrealized gains	0	0
Gross unrealized losses	(5)	(9)
Fair value	$ 995	$ 995

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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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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://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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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.

+ 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 210.5-02.2)
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