Note 8 - Investments in Marketable Securities (Details Textual) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2024	Dec. 31, 2022	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Marketable Securities, Accumulated Unrealized Gain (Loss)	$ 157,909,000		$ 157,909,000		$ 157,909,000		$ 137,716,000
Marketable Security, Unrealized Gain (Loss)			5,503,000	$ 8,644,000	20,193,000	$ 32,669,000	32,669,000
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale	40,579,000	$ 2,826,000			40,579,000	2,826,000
Marketable Security, Realized Gain (Loss)	14,261,000		14,261,000		14,261,000	422,000
Debt Instrument, Face Amount	29,421,000		$ 29,421,000		29,421,000		$ 75,000,000
Proceeds from (Repayments of) Notes Payable					45,579,000
Marketable Securities, Realized Gain (Loss)		422,000
Borrowed Funds from Margin Loan Account		6,011,000
Payments to Acquire Marketable Securities		$ 10,001,000				10,001,000
Repayments of Other Long-Term Debt				$ 11,000	$ 45,579,000	$ 11,000
Proceeds from Equity Method Investment, Distribution	$ 2,978,000