Note 2 - Summary of Significant Accounting Policies - Investment in Financial Instruments (Details) - USD ($)	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Marketable securities, fair value	$ 194,581,000
Marketable securities, gross unrealized gains	140,692,000
Common Stock [Member]
Marketable securities, fair value	194,581,000	$ 212,296,000
Marketable securities, amortized cost	53,889,000	53,889,000
Marketable securities, gross unrealized gains	$ 140,692,000	$ 158,407,000

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=99377092&loc=SL75136599-209740

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

+ References

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- Definition

Amount of unrealized gain (loss) on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117546-209714

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