Note 3 - Cash, Cash Equivalents and Investments  | 
9 Months Ended | ||||||||||||||||||||||||||||||||||||
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Jun. 30, 2017  | |||||||||||||||||||||||||||||||||||||
| Notes to Financial Statements | |||||||||||||||||||||||||||||||||||||
| Cash and Cash Equivalents Disclosure [Text Block] | 
 Note  3.  Cash, Cash Equivalents and InvestmentsThe Company currently invests its excess cash in money market accounts and bank certificates of deposit (CDs) with a term of   and are carried at amortized cost. Investments maturing in less than not  more than five  years. CDs with original maturities of more than three  months are reported as held-to-maturity investmentsone  year are classified as short term investments on the balance sheet, and investments maturing in one  year or greater are classified as long term investments on the balance sheet. The maturity dates of the Company’s CDs at  
 June 30, 2017  and  September 30, 2016  are as follows:
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