Note 2 - Summary of Significant Accounting Policies - Allowance for Doubtful Accounts (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2015
Balance at beginning of year	$ 200,000	$ 250,000	$ 250,000
Additions charged to costs and expenses	33,000	5,000	61,000
Accounts charged off less recoveries	(33,000)	(55,000)	(61,000)
Balance at end of year	$ 200,000	$ 200,000	$ 250,000