Note 2 - Investments - Schedule of Carrying Value and Fair Value of Securities Available-for-sale (Details) - USD ($)	Oct. 31, 2024	Apr. 30, 2024
Due within 1 year, amortized cost	$ 33,935,000	$ 42,843,000
Due within 1 year, gross unrealized gains	43,000	4,000
Due within 1 year, gross unrealized losses	(1,000)	(61,000)
Due within 1 year, fair value	33,977,000	42,786,000
Due 1 year through 5 years, amortized cost	5,073,000	5,088,000
Due 1 year through 5 years, gross unrealized gains	0	0
Due within 1 year, gross unrealized gains	0	0
Due 1 year through 5 years, gross unrealized losses	(135,000)	(263,000)
Due 1 year through 5 years	4,938,000	4,825,000
Amortized cost	39,008,000	47,931,000
Total investment in government debt securities, gross unrealized gains	43,000	4,000
Total investment in government debt securities, gross unrealized losses	(136,000)	(324,000)
Fair value	$ 38,915,000	$ 47,611,000