Note 2 - Investments (Details Textual) - USD ($)	3 Months Ended				6 Months Ended		12 Months Ended
	Oct. 31, 2023	Jul. 31, 2023	Oct. 31, 2022	Jul. 31, 2022	Oct. 31, 2023	Oct. 31, 2022	Apr. 30, 2023
Equity Securities, FV-NI, Cost	$ 10,146,000				$ 10,146,000		$ 10,169,000
Equity Securities, FV-NI	13,064,000				13,064,000		14,546,000
Proceeds from Sale of Equity Securities, FV-NI					999,000	$ 1,016,000
Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent	(448,000)	$ (212,000)	$ (3,000)	$ 5,000	(660,000)	2,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax					(177,000)	1,000
Equity Securities, FV-NI, Gain (Loss)					(18,000)	(9,000)
Equity Method Investments	59,119,000				59,119,000		58,775,000
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	2,967,000				2,967,000		2,601,000
Fixed Income Securities [Member]
Proceeds from Sale and Maturity of Debt Securities, Available-for-Sale					19,265,000	$ 0
AOCI, Debt Securities, Available-for-Sale, Adjustment, after Tax	$ 363,000				363,000		473,000
Other Comprehensive Income (Loss), Available-for-Sale Securities Adjustment, Net of Tax, Portion Attributable to Parent					$ 837,000		503,000
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, Tax							$ 105,000
Debt Securities, Available-for-Sale, Weighted Average Yield	3.65%				3.65%		2.55%
Fixed Income Securities [Member] | AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-Sale, Parent [Member]
AOCI Tax, Attributable to Parent	$ 77,000				$ 77,000		$ 99,000