Note 8 - Income Taxes - Summary of Differences Between U.S. Federal Statutory Rate and Company's Effective Tax Rate (Details)	12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Statutory tax rate	21.00%	21.00%	34.00%
State income taxes, net of U.S. federal tax benefit	6.60%	8.10%	3.30%
Return to accrual adjustment	(0.60%)	(0.10%)	(0.70%)
Tax credits		0.50%	0.60%
Charges without tax benefit	(5.30%)	(4.30%)	(11.80%)
Change in statutory rate		(10.30%)
Valuation allowance	(22.10%)	(50.40%)
Other exclusions	0.70%	(0.10%)	(0.10%)
Company’s effective tax rate	0.30%	(35.60%)	25.30%