Note 6 - Income Taxes - Summary of the Difference Between Statutory Federal Income Tax Rate and Effective Rate (Details)	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024
Statutory federal income tax rate	21.00%	21.00%
State franchise taxes (net of federal tax benefit)	4.80%	5.00%
Effect of state rate change on beginning balance of deferred tax liabilities	(0.30%)	(0.40%)
Dividends received deduction	(0.30%)	(0.50%)
Others	0.10%	0.00%
Effective tax rate	25.30%	25.10%