Note 2 - Investments (Details Textual) $ / shares in Units, shares in Millions			3 Months Ended		6 Months Ended
		Jan. 12, 2021 USD ($)	Dec. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($)	Dec. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($)	Jun. 30, 2024 USD ($)	Mar. 31, 2021 shares	Jan. 31, 2021 USD ($) $ / shares	Jan. 31, 2021 $ / shares
Investment Owned, Fair Value			$ 14,000,000		$ 14,000,000
Investment Owned, Cost			$ 17,000,000		$ 17,000,000
Value of Fair Value Investments to Company Assets, Percent			27.90%		27.90%
Equity Securities without Readily Determinable Fair Value, Amount			$ 1,687,000	$ 1,613,000	$ 1,687,000	$ 1,613,000	$ 1,687,000
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss	[1]		926,000		926,000		868,000
Accounts and Financing Receivable, after Allowance for Credit Loss, Current			750,000		750,000		0
Interest Receivable			51,000		51,000		13,000
Accounts, Notes, and Loans Receivable, Allowance for Credit Loss, Current			0		0		0
Debt Securities, Available-for-Sale, Total	[2]		3,037,000		3,037,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax			1,000	68,000	19,000	120,000
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Period Increase (Decrease)			35,000	28,000	58,000	55,000
Debt Securities, Available-for-Sale, Periodic Principal Payments			750,000
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		2,500,000
Realized Gain (Loss) on Principal Payment Proceeds			170,000	303,000	373,000	$ 639,000
Equity Securities Without Readily Determinable Fair Values, Unrealized Gain (Loss)				$ 775,000
Warrants and Convertible Debentures [Member]
Accounts and Financing Receivable, after Allowance for Credit Loss, Current			750,000		750,000		0
Interest Receivable			26,000		26,000
Accounts, Notes, and Loans Receivable, Allowance for Credit Loss, Current			0		0		0
U S Global Investors Funds [Member]
Investment Owned, Fair Value			10,500,000		10,500,000		10,500,000
HIVE Blockchain Technologies Ltd. [Member] | Convertible Securities [Member]
Investment Owned, Balance, Principal Amount									$ 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			3,000,000		3,000,000		4,400,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member]
Investment Owned, Balance, Principal Amount			3,100,000		3,100,000
Debt Securities, Available-for-Sale, Total			$ 3,000,000		$ 3,000,000		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.