Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($)	Mar. 31, 2020	Sep. 30, 2019
Short-term marketable securities	$ 3,464,834	$ 3,695,364
Long-term Securities	1,646,466	1,384,819
Fair Value, Nonrecurring [Member]
Cost Basis	5,407,488	5,344,359
Unrealized Gains (Losses)	184	11,362
Fair Value	5,407,672	5,355,721
Cash Equivalents	296,372	275,538
Short-term marketable securities	3,464,834	3,695,364
Long-term Securities	1,646,466	1,384,819
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Cost Basis	296,372	275,538
Unrealized Gains (Losses)
Fair Value	296,372	275,538
Cash Equivalents	296,372	275,538
Short-term marketable securities
Long-term Securities
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Cost Basis	5,111,116	5,068,821
Unrealized Gains (Losses)	184	11,362
Fair Value	5,111,300	5,080,183
Cash Equivalents
Short-term marketable securities	3,464,834	3,695,364
Long-term Securities	1,646,466	1,384,819
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Certificates of Deposit [Member]
Cost Basis	1,943,752	971,592
Unrealized Gains (Losses)
Fair Value	1,943,752	971,592
Cash Equivalents
Short-term marketable securities	499,000	499,000
Long-term Securities	1,444,752	472,592
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Cost Basis	612,308	240,463
Unrealized Gains (Losses)	525	205
Fair Value	612,833	240,668
Cash Equivalents
Short-term marketable securities	612,833	80,336
Long-term Securities		160,332
Fair Value, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Cost Basis	2,555,056	3,856,766
Unrealized Gains (Losses)	(341)	11,157
Fair Value	2,554,715	3,867,923
Cash Equivalents
Short-term marketable securities	2,353,001	3,116,028
Long-term Securities	$ 201,714	$ 751,895

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount before tax of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Amount of investment in marketable security, classified as current.

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Amount of investment in marketable security, classified as noncurrent.

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