Note 6 - Investments in Marketable Securities - Summary of Investments (Details) - USD ($)	Jun. 30, 2019	Sep. 30, 2018
Aggregate fair value	$ 195,367,000	$ 212,296,000
Amortized/Adjusted cost basis	53,889,000	53,889,000
Pretax unrealized gains	$ 141,478,000	$ 158,407,000

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant