Note 8 - Investments in Marketable Securities (Details Textual) - USD ($)	1 Months Ended		3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2022
Marketable Securities, Accumulated Unrealized Gain (Loss)	$ 144,717,000		$ 144,717,000		$ 120,692,000
Marketable Securities, Unrealized Gain (Loss)			24,025,000	$ (36,088,000)
Marketable Securities, Unrealized Gain (Loss)			(24,025,000)	36,088,000
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale, Total	2,826,000	$ 50,020,000	2,826,000	50,020,000
Marketable Securities, Realized Gain (Loss)	422,000	46,694,000	422,000	46,694,000
Borrowed Funds from Margin Loan Account	6,011,000	37,014,000
Payments to Acquire Marketable Securities	$ 10,001,000	$ 87,125,000	$ 10,001,000	$ 87,125,000