Note 8 - Investments in Marketable Securities (Details Textual) - USD ($)	1 Months Ended	3 Months Ended			12 Months Ended
	Dec. 31, 2022	Dec. 31, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2023
Marketable Securities, Accumulated Unrealized Gain (Loss)		$ 152,406,000			$ 137,716,000
Marketable Security, Unrealized Gain (Loss)		14,690,000		$ 24,025,000	(24,025,000)
Marketable Security, Unrealized Gain (Loss)		(14,690,000)		(24,025,000)	$ 24,025,000
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale, Total	$ 2,826,000			2,826,000
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		$ 5,000,000	$ 11,000