Note 4 - Investments (Details Textual) $ / shares in Units, shares in Millions			3 Months Ended		12 Months Ended
		Jan. 12, 2021 USD ($)	Jun. 30, 2023 USD ($) shares		Jun. 30, 2023 USD ($) shares		Jun. 30, 2022 USD ($) $ / shares	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2023 $ / shares	Jun. 30, 2021 $ / shares shares
Investment Owned, Fair Value			$ 20,200,000		$ 20,200,000
Investment Owned, Cost			$ 27,300,000		$ 27,300,000
Value of Fair Value Investments to Company Assets, Percent			36.30%		36.30%
Equity Securities without Readily Determinable Fair Value, Amount			$ 2,388,000		$ 2,388,000		$ 3,992,000
Debt Securities, Held-to-Maturity, Amortized Cost, before Allowance for Credit Loss, Total			1,000,000		1,000,000		1,000,000
Equity Securities, FV-NI, Total			13,205,000		13,205,000		14,300,000
Debt Securities, Available-for-Sale, Total	[1]		7,008,000	[2]	7,008,000	[2]	10,625,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax					(961,000)		(1,209,000)
Debt Securities, Held-to-Maturity, Accumulated Unrecognized Loss	[3]		232,000		232,000		133,000
Debt Securities, Available-for-Sale, Periodic Principal Payments			750,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Cumulative Amount			2,500,000		2,500,000
Equity Securities without Readily Determinable Fair Value, Downward Price Adjustment, Cumulative Amount			3,800,000		3,800,000
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount					14,000		187,000
Income (Loss) from Equity Method Investments					0		(206,000)
Realized Gain (Loss) on Principal Payment Proceeds					1,700,000		2,200,000
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment from AOCI, Realized upon Sale or Liquidation, Net of Tax					(0)		10,000
Equity Securities Without Readily Determinable Fair Values, Unrealized Gain (Loss)					(2,300,000)		187,000
U S Global Investors Funds [Member]
Investment Owned, Fair Value			12,400,000		12,400,000		12,800,000
HIVE Blockchain Technologies Ltd. [Member]
Investment Owned, Fair Value			7,300,000		7,300,000		11,100,000
Realized Gain (Loss) on Principal Payment Proceeds					1,700,000		2,200,000
HIVE Blockchain Technologies Ltd. [Member] | Convertible Securities [Member]
Investment Owned, Balance, Principal Amount		$ 15,000,000	7,600,000		7,600,000
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			7,300,000		7,300,000		11,100,000
HIVE Blockchain Technologies Ltd. [Member] | Unsecured Convertible Debentures [Member]
Debt Securities, Available-for-Sale, Total		16,000,000	$ 7,000,000		$ 7,000,000		$ 10,600,000
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] | Convertible Debt Securities [Member]
Debt Instrument, Interest Rate, Stated Percentage								8.00%		8.00%
Debt Instrument, Convertible, Conversion Price (in dollars per share) | $ / shares							$ 11.7	$ 2.34
HIVE Blockchain Technologies Ltd. [Member] | Common Shares Purchase Warrants [Member]
Investment, Common Share Purchase Warrants (in shares) | shares			5		5			5		5
Class of Warrant or Right, Exercise Price of Warrants or Rights (in CAD per share) | $ / shares									$ 15	$ 3
Equity Securities, FV-NI, Total		$ 5,900,000	$ 290,000		$ 290,000		$ 515,000
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
Equity Securities without Readily Determinable Fair Value, Upward Price Adjustment, Annual Amount							187,000
Investment Owned, Direct Percentage			2.80%		2.80%
Galileo New Economy Fund L P [Member]
Equity Method Investment, Ownership Percentage								22.00%		22.00%
Income (Loss) from Equity Method Investments							(206,000)
Galileo New Economy Fund L P [Member] | Cash [Member]
Proceeds from Equity Method Investment, Distribution, Return of Capital								$ 85,000
Galileo New Economy Fund L P [Member] | Common Shares [Member]
Proceeds from Equity Method Investment, Distribution, Return of Capital							$ 228,000

[1] Changes in unrealized gains and losses are included in the statement of comprehensive income (loss), except for embedded derivatives. Changes in unrealized and realized gains and losses for embedded derivatives are included in earnings in the statement of operations.

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

[3] Held-to-maturity debt instruments are carried at amortized cost, and the fair value is classified as Level 2 according to the fair value hierarchy.