Note 6 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($)	Mar. 31, 2018	Sep. 30, 2017
Short-term marketable securities	$ 4,063,109	$ 4,359,542
Long-term marketable securities	991,178	711,124
Fair Value, Measurements, Nonrecurring [Member]
Cost Basis	5,170,963	5,127,192
Unrealized Gains (Losses)	(18,138)	(1,269)
Fair Value	5,152,826	5,125,923
Cash Equivalents	98,539	55,257
Short-term marketable securities	4,063,109	4,359,542
Long-term marketable securities	991,178	711,124
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Cost Basis	98,539	55,257
Unrealized Gains (Losses)
Fair Value	98,539	55,257
Cash Equivalents	98,539	55,257
Short-term marketable securities
Long-term marketable securities
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Cost Basis	5,072,424	5,071,935
Unrealized Gains (Losses)	(18,138)	(1,269)
Fair Value	5,054,287	5,070,666
Cash Equivalents
Short-term marketable securities	4,063,109	4,359,542
Long-term marketable securities	991,178	711,124
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Certificates of Deposit [Member]
Cost Basis	936,952	2,436,647
Unrealized Gains (Losses)
Fair Value	936,952	2,436,647
Cash Equivalents
Short-term marketable securities	437,952	1,937,647
Long-term marketable securities	499,000	499,000
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| US States and Political Subdivisions Debt Securities [Member]
Cost Basis	85,626	25,315
Unrealized Gains (Losses)	(168)	(12)
Fair Value	85,459	25,303
Cash Equivalents
Short-term marketable securities	85,459	25,303
Long-term marketable securities
Fair Value, Measurements, Nonrecurring [Member] \| Fair Value, Inputs, Level 2 [Member] \| Corporate Debt Securities [Member]
Cost Basis	4,049,846	2,609,973
Unrealized Gains (Losses)	(17,970)	(1,257)
Fair Value	4,031,876	2,608,716
Cash Equivalents
Short-term marketable securities	3,539,698	2,396,592
Long-term marketable securities	$ 492,178	$ 212,124

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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-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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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
-Topic 320
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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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-Topic 210
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Amount of investment in marketable security, classified as noncurrent.

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