Note 7 - Stock-based Compensation - Option Transaction Summary (Details) - $ / shares |
6 Months Ended | |
|---|---|---|
Mar. 31, 2023 |
Mar. 31, 2022 |
|
| Outstanding as of September 30, 2022 (in shares) | 236,509 | |
| Outstanding as of September 30, 2022 (in dollars per share) | $ 31.30 | |
| Granted (in shares) | 19,084 | 62,730 |
| Granted (in dollars per share) | $ 95.06 | $ 66.48 |
| Exercised (in shares) | (18,709) | |
| Exercised (in dollars per share) | $ 27.24 | |
| Forfeited or Expired (in shares) | 0 | |
| Forfeited or Expired (in dollars per share) | $ 0 | |
| Outstanding as of March 31, 2023 (in shares) | 236,884 | |
| Outstanding as of March 31, 2023 (in dollars per share) | $ 36.76 | |
| X | ||||||||||
- Definition For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Weighted average price of options that were either forfeited or expired. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- Definition Gross number of share options (or share units) granted during the period. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Number of options outstanding, including both vested and non-vested options. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Weighted average price at which option holders acquired shares when converting their stock options into shares. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Number of share options (or share units) exercised during the current period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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