Note 14 - Stock Option Plans - Summary of Outstanding Options (Details) - $ / shares
 6 Months Ended
Mar. 31, 2020
Dec. 31, 2019
Sep. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Options Outstanding, Number of Shares Outstanding (in shares) 666,867 670,167 722,567 726,767 728,533 728,867
Options Outstanding, Weighted Average Remaining Contractual Life (Year) 2 years 182 days          
Options Outstanding, Weighted Average Exercise Price (in dollars per share) $ 8.19 $ 8.19 $ 8.18 $ 8.17 $ 8.17 $ 8.17
Options Exercisable, Number of Shares Exercisable (in shares) 666,867     726,767    
Options Exercisable, Weighted Average Exercise Price (in dollars per share) $ 8.19     $ 8.17    
Range One [Member]            
Range of Exercise Price, Lower (in dollars per share) 5.7501          
Range of Exercise Price, Upper (in dollars per share) $ 8.625          
Options Outstanding, Number of Shares Outstanding (in shares) 557,367          
Options Outstanding, Weighted Average Remaining Contractual Life (Year) 2 years 146 days          
Options Outstanding, Weighted Average Exercise Price (in dollars per share) $ 7.96          
Options Exercisable, Number of Shares Exercisable (in shares) 557,367          
Options Exercisable, Weighted Average Exercise Price (in dollars per share) $ 7.96          
Range Two [Member]            
Range of Exercise Price, Lower (in dollars per share) 8.6251          
Range of Exercise Price, Upper (in dollars per share) $ 11.50          
Options Outstanding, Number of Shares Outstanding (in shares) 109,500          
Options Outstanding, Weighted Average Remaining Contractual Life (Year) 2 years 292 days          
Options Outstanding, Weighted Average Exercise Price (in dollars per share) $ 9.37          
Options Exercisable, Number of Shares Exercisable (in shares) 109,500          
Options Exercisable, Weighted Average Exercise Price (in dollars per share) $ 9.37