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Employee Stock Purchase and Stock Option Plans (Stock Issuance Activity Under the 1989 ESPP and the GESPP) (Details) - USD ($)		12 Months Ended
	Jan. 19, 2017	Sep. 27, 2019	Sep. 28, 2018	Sep. 29, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Discount (percent) available to employees on the purchase of common stock		5.00%
Aggregate Purchase Price Paid for Shares Sold:		$ 27,295,425	$ 23,831,467	$ 23,190,491
Aggregate Number of Shares Sold:		389,423	394,304	443,300
Number of remaining shares reserved for issuance at September 27, 2019 (in shares)		6,146,619
Under the 1989 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate Purchase Price Paid for Shares Sold:		$ 24,824,232	$ 21,590,858	$ 21,084,657
Aggregate Number of Shares Sold:		354,580	357,899	403,652
Increase in number of shares authorized	4,350,000
Number of remaining shares reserved for issuance at September 27, 2019 (in shares)		3,833,375
Under the GESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate Purchase Price Paid for Shares Sold:		$ 2,471,193	$ 2,240,609	$ 2,105,834
Aggregate Number of Shares Sold:		34,843	36,405	39,648
Increase in number of shares authorized	150,000
Number of remaining shares reserved for issuance at September 27, 2019 (in shares)		103,732

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.29)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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