Note 8 - Investments in Marketable Securities (Details Textual) - USD ($)	1 Months Ended			3 Months Ended		6 Months Ended
	Mar. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022	Sep. 30, 2022
Marketable Securities, Accumulated Unrealized Gain (Loss)	$ 153,361,000			$ 153,361,000		$ 153,361,000		$ 120,692,000
Marketable Security, Unrealized Gain (Loss)				8,644,000	$ (8,321,000)	32,669,000	$ (44,409,000)
Marketable Security, Unrealized Gain (Loss)				(8,644,000)	8,321,000	(32,669,000)	44,409,000
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale, Total		$ 2,826,000	$ 80,570,000			2,826,000	80,570,000
Marketable Securities, Realized Gain (Loss)		422,000	14,249,000	$ 0	$ (32,445,000)	422,000	14,249,000
Borrowed Funds from Margin Loan Account		6,011,000	43,014,000
Payments to Acquire Marketable Securities		$ 10,001,000	$ 117,678,000			10,001,000	117,678,000
Repayments of Other Long-Term Debt						11,000	$ 14,000
Proceeds from Equity Method Investment, Distribution	$ 2,978,000					$ 2,978,000