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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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