Note 11 - Other Comprehensive Income (Loss) - Schedule of Other Comprehensive Income and Loss (Details) - USD ($) |
3 Months Ended | 9 Months Ended | ||||||
|---|---|---|---|---|---|---|---|---|
Jun. 30, 2026 |
Mar. 31, 2026 |
Dec. 31, 2025 |
Jun. 30, 2025 |
Mar. 31, 2025 |
Dec. 31, 2024 |
Jun. 30, 2026 |
Jun. 30, 2025 |
|
| Unrealized gains (losses), before tax | $ 506,950 | $ (20,816) | $ 1,132,692 | $ 507,492 | ||||
| Unrealized gains (losses), tax | (130,489) | 5,358 | (291,556) | (130,628) | ||||
| Unrealized gains (losses), after tax | 376,461 | (15,458) | 841,136 | 376,864 | ||||
| Transfer of realized gains to interest expense, before tax | (231,048) | (323,513) | (829,579) | (1,034,976) | ||||
| Transfer of realized gains to interest expense, tax | 59,473 | 83,273 | 213,535 | 266,403 | ||||
| Transfer of realized gains to interest expense, after tax | (171,575) | (240,240) | (616,044) | (768,573) | ||||
| Net interest rate swaps, before tax | 275,902 | (344,329) | 303,113 | (527,484) | ||||
| Net interest rate swaps, tax | (71,016) | 88,631 | (78,021) | 135,775 | ||||
| Net interest rate swaps, after tax | 204,886 | (255,698) | 225,092 | (391,709) | ||||
| Amortization of net actuarial gains, before tax | (7,829) | (10,379) | (23,487) | (31,134) | ||||
| Amortization of net actuarial gains, tax | 2,015 | 2,671 | 6,045 | 8,013 | ||||
| Amortization of net actuarial gains, after tax | (5,814) | (7,708) | (17,442) | (23,121) | ||||
| Other comprehensive income (loss), before tax | 268,073 | (354,708) | 279,626 | (558,618) | ||||
| Other comprehensive income (loss), tax | (69,001) | 91,302 | (71,976) | 143,788 | ||||
| Other comprehensive income (loss), after tax | $ 199,072 | $ 135,495 | $ (126,917) | $ (263,406) | $ (373,852) | $ 222,428 | $ 207,650 | $ (414,830) |
| X | ||||||||||
- Definition Amount before tax of other comprehensive income (loss) attributable to parent entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount, after tax and reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, before tax and after reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, after reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount, before tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/exampleRef
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| X | ||||||||||
- Definition Amount of tax expense (benefit) for reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness. Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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| X | ||||||||||
- Definition Amount after tax of other comprehensive income (loss) attributable to parent entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount, before tax, of reclassification adjustment from accumulated other comprehensive (income) loss for net period benefit cost (credit) of defined benefit plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount, after tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of tax (expense) benefit for reclassification adjustment from accumulated other comprehensive (income) loss of defined benefit plan. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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