Note 6 - Investments in Marketable Securities - Summary of Investments (Details) - USD ($)	Dec. 31, 2017	Sep. 30, 2017
Aggregate fair value	$ 244,934,000	$ 229,265,000
Amortized/Adjusted cost basis	63,394,000	63,393,000
Pretax unrealized gains	181,540,000	165,872,000
Equity Securities [Member]
Aggregate fair value	236,387,000	220,973,000
Amortized/Adjusted cost basis	58,449,000	58,449,000
Pretax unrealized gains	177,938,000	162,524,000
Debt Securities [Member]
Aggregate fair value	8,547,000	8,292,000
Amortized/Adjusted cost basis	4,945,000	4,944,000
Pretax unrealized gains	$ 3,602,000	$ 3,348,000