Note 4 - Investments (Details Textual) - USD ($) $ / shares in Units, shares in Millions				1 Months Ended	12 Months Ended
		Jan. 01, 2024	Jan. 12, 2021	Jan. 31, 2024	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024	Mar. 31, 2021	Jan. 31, 2021
Income Statement [Abstract]
Investment Income, Net					$ 2,144,000	$ 316,000
Investment Owned, Fair Value					15,500,000
Investment Owned, Cost					$ 18,000,000
Value of Fair Value Investments to Company Assets, Percent					29.80%
Equity Securities without Readily Determinable Fair Value, Amount					$ 1,687,000	2,388,000
Debt Securities, Held-to-Maturity, Amortized Cost, after Allowance for Credit Loss	[1]				868,000	1,000,000
Debt Securities, Available-for-Sale, Total	[2]				4,414,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax					136,000	(961,000)
Equity Securities, FV-NI					10,885,000	13,205,000
Equity Securities, FV-NI					10,885,000	13,205,000
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)					(102,000)
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment and Tax					172,000
Debt Securities, Held-to-Maturity, Allowance for Credit Loss, Period Increase (Decrease)					(100,000)
Debt Securities, Available-for-Sale, Periodic Principal Payments					750,000
Interest Receivable					13,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Cumulative Amount					2,500,000
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Cumulative Amount					5,000,000
Realized Gain (Loss) on Principal Payment Proceeds					1,100,000	1,700,000
Equity Securities Without Readily Determinable Fair Values, Unrealized Gain (Loss)					$ (1,000,000)	(2,300,000)
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]					Investment Income, Net
Fair Value, Inputs, Level 3 [Member]
Equity Securities, FV-NI					$ 0	290,000
Equity Securities, FV-NI					0	290,000
Warrant [Member]
Equity Securities, FV-NI			$ 5,900,000			290,000
Equity Securities, FV-NI			5,900,000			290,000
Warrant [Member] | Investment Income, Net
Equity Securities, FV-NI, Realized Loss				$ 5,900,000
U S Global Investors Funds [Member]
Investment Owned, Fair Value					10,500,000	12,400,000
HIVE Blockchain Technologies Ltd. [Member]
Income Statement [Abstract]
Investment Income, Net					854,000	1,200,000
Investment Owned, Fair Value					4,400,000	7,300,000
Realized Gain (Loss) on Principal Payment Proceeds					1,100,000	1,700,000
HIVE Blockchain Technologies Ltd. [Member] | Convertible Securities [Member]
Investment Owned, Balance, Principal Amount					4,600,000				$ 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					4,400,000	7,300,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member]
Debt Securities, Available-for-Sale, Total					$ 4,400,000	7,000,000
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)					$ 11.7				$ 2.34
HIVE Blockchain Technologies Ltd. [Member] | Common Shares Purchase Warrants [Member]
Investment, Common Share Purchase Warrants (in shares)								5
HIVE Blockchain Technologies Ltd. [Member] | Warrant [Member]
Equity Securities, FV-NI				5,900,000
Equity Securities, FV-NI				$ 5,900,000
Equity Securities, FV-NI, Realized Loss		$ 5,900,000
The Sonar Company [Member]
Equity Securities without Readily Determinable Fair Value, Amount					$ 362,000	$ 362,000
Other Investments and Securities, at Cost					$ 175,000
Investment Owned, Direct Percentage							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.