| Note 3 - Investments (Details Textual) | 12 Months Ended | |
|---|---|---|
| Sep. 30, 2023  USD ($) | Sep. 30, 2022  USD ($) | |
| Proceeds from Sale, Maturity and Collection of Investments | $ 0 | $ 14,365,000 | 
| debt Securities, Realized Gain | 92,000 | |
| Debt Securities, Realized Loss | $ 53,000 | |
| Debt Securities, Available-for-Sale, Unrealized Loss Position, Number of Positions | 42 | |
| Debt Securities, Available for Sale, Other than Temporary Impairment | $ 0 | |
| X | ||||||||||
| 
- Definition Represents other than temporary impairment of debt securities available for sale. No definition available. 
 | 
| X | ||||||||||
| 
- Definition Amount of gain realized on sale of debt securities. No definition available. 
 | 
| X | ||||||||||
| 
- Definition Amount of loss realized on sale of debt securities. No definition available. 
 | 
| X | ||||||||||
| 
- Definition Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset. Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef 
 | 
| X | ||||||||||
| 
- Definition The cash inflow associated with the sale, maturity and collection of all investments such as debt, security and so forth during the period. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
 |