Note 2 - Investments (Details Textual) - USD ($)	3 Months Ended						9 Months Ended
	Jan. 31, 2025	Oct. 31, 2024	Jul. 31, 2024	Jan. 31, 2024	Oct. 31, 2023	Jul. 31, 2023	Jan. 31, 2025	Jan. 31, 2024	Apr. 30, 2024
Equity Securities, FV-NI, Cost	$ 15,509,000						$ 15,509,000		$ 11,663,000
Equity securities	21,808,000						21,808,000		16,344,000
Proceeds from Sale of Equity Securities, FV-NI							3,173,000	$ 1,129,000
Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	(7,000)	$ 2,000	$ 177,000	$ 258,000	$ (448,000)	$ (212,000)	172,000	(402,000)
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax							46,000	(106,000)
Equity Securities, FV-NI, Gain (Loss)							(124,000)	(16,000)
Equity Method Investments	61,124,000						61,124,000		60,134,000
EAM Trust [Member]
Fair Value of Contributed Capital at Inception	55,805,000						55,805,000		55,805,000
Cash and Liquid Securities in Excess of Working Capital Requirements Contributed to Capital Account	5,820,000						5,820,000		5,820,000
Equity Method Investment, Other than Temporary Impairment							$ 0	0
Percentage of Non Voting Profit Interest							50.00%
Accrued Non Voting Revenues and Non Voting Profits Interests Payable	4,855,000						$ 4,855,000		3,865,000
Fixed Income Securities [Member]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale							38,469,000	32,113,000
AOCI, Debt Securities, Available-for-Sale, Adjustment, after Tax	$ (102,000)						(102,000)		$ (320,000)
Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent							(218,000)	(793,000)
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax							$ 46,000	$ (166,000)
Debt Securities, Available-for-Sale, Weighted Average Yield	4.70%						4.70%		4.40%
Fixed Income Securities [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
AOCI Tax, Attributable to Parent	$ (22,000)						$ (22,000)		$ (67,000)