Note 2 - Summary of Significant Accounting Policies - Investment in Financial Instruments (Details) - USD ($)	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Marketable securities, fair value	$ 229,265,000	$ 166,634,000
Marketable securities, amortized cost	63,393,000	58,378,000
Marketable securities, gross unrealized gains	165,872,000	108,256,000
Common Stock [Member]
Marketable securities, fair value	220,973,000	158,462,000
Marketable securities, amortized cost	58,449,000	53,436,000
Marketable securities, gross unrealized gains	162,524,000	105,026,000
Fixed Income Securities [Member]
Marketable securities, fair value	8,292,000	8,172,000
Marketable securities, amortized cost	4,944,000	4,942,000
Marketable securities, gross unrealized gains	$ 3,348,000	$ 3,230,000