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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. 29, 2017 | Sep. 30, 2016 | Oct. 02, 2015
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 |  | $ 23,190,491 | $ 26,291,308 | $ 32,157,279
Aggregate Number of Shares Sold |  | 443,300 | 627,657 | 781,214
Shares reserved for future Issuance (in shares) |  | 10,181,183 |  |
Under the 1989 ESPP |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Aggregate Purchase Price Paid for Shares Sold |  | $ 21,084,657 | $ 23,631,241 | $ 28,621,800
Aggregate Number of Shares Sold |  | 403,652 | 564,461 | 696,853
Increase in number of shares authorized | 4,350,000 |  |  |
Shares reserved for future Issuance (in shares) |  | 4,545,854 |  |
Under the GESPP |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |
Aggregate Purchase Price Paid for Shares Sold |  | $ 2,105,834 | $ 2,660,067 | $ 3,535,479
Aggregate Number of Shares Sold |  | 39,648 | 63,196 | 84,361
Increase in number of shares authorized | 150,000 |  |  |
Shares reserved for future Issuance (in shares) |  | 174,980 |  |

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- Definition Aggregate number of common shares reserved for future issuance. + 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 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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