Note 2 - Investments (Details Textual) $ / shares in Units, shares in Millions			3 Months Ended		15 Months Ended
		Jan. 12, 2021 USD ($)	Sep. 30, 2024 USD ($) $ / shares	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) $ / shares	Jun. 30, 2024 USD ($)	Mar. 31, 2021 shares	Jan. 31, 2021 USD ($) $ / shares	Jan. 31, 2021 $ / shares
Investment Owned, Fair Value			$ 14,900,000		$ 14,900,000
Investment Owned, Cost			$ 17,500,000		$ 17,500,000
Value of Fair Value Investments to Company Assets, Percent			29.20%		29.20%
Equity Securities without Readily Determinable Fair Value, Amount			$ 1,687,000	$ 1,613,000	$ 1,687,000	$ 1,687,000
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss	[1]		891,000		891,000	868,000
Debt Securities, Available-for-Sale, Total	[2]		3,742,000		3,742,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax			18,000	51,000
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Period Increase (Decrease)			(23,000)		(27,000)
Debt Securities, Available-for-Sale, Periodic Principal Payments			750,000
Interest Receivable			25,000		25,000	13,000
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Cumulative Amount			5,000,000		5,000,000	1,700,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Cumulative Amount						2,500,000
Realized Gain (Loss) on Principal Payment Proceeds			203,000	336,000
Equity Securities Without Readily Determinable Fair Values, Unrealized Gain (Loss)				$ 775,000
U S Global Investors Funds [Member]
Investment Owned, Fair Value			10,600,000		10,600,000	10,500,000
HIVE Blockchain Technologies Ltd. [Member] | Convertible Securities [Member]
Investment Owned, Balance, Principal Amount			3,800,000		3,800,000			$ 15,000,000
HIVE Blockchain Technologies Ltd. [Member] | Warrants and Convertible Debentures [Member] | Fair Value, Inputs, Level 3 [Member] | Available-for-sale Securities and Equity Securities [Member]
Investment Owned, Fair Value			3,700,000		3,700,000	4,400,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member]
Debt Securities, Available-for-Sale, Total			$ 3,700,000		$ 3,700,000	4,400,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax		$ 6,900,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member] | Estimate of Fair Value Measurement [Member]
Debt Securities, Available-for-Sale, Total		$ 16,000,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member] | Convertible Debt Securities [Member]
Debt Instrument, Interest Rate, Stated Percentage							8.00%
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares			$ 11.7		$ 11.7			$ 2.34
HIVE Blockchain Technologies Ltd. [Member] | Common Shares Purchase Warrants [Member]
Investment, Common Share Purchase Warrants (in shares) | shares							5
Class of Warrant or Right, Exercise Price of Warrants or Rights (in CAD per share) | $ / shares									$ 3
The Sonar Company [Member]
Equity Securities without Readily Determinable Fair Value, Amount			$ 362,000		$ 362,000	$ 362,000
Other Investments and Securities, at Cost			$ 175,000		$ 175,000
Investment Owned, Direct Percentage			2.80%		2.80%

[1] Held-to-maturity debt instruments are carried at amortized cost, net of allowance for credit losses, and the fair value is classified as Level 2 according to the fair value hierarchy.

[2] Principal payments of $750,000 are due quarterly with a final maturity in January 2026.