Note 1 - Organization and Summary of Significant Accounting Policies - Schedule of Fair Value Measurements of Investments (Details) - USD ($)	Jan. 31, 2025	Apr. 30, 2024
Cash equivalents	$ 26,005,000	$ 4,136,000
Equity securities	21,808,000	16,344,000
Available-for-sale fixed income securities	27,167,000	47,611,000
Investments, Fair Value Disclosure	74,980,000	68,091,000
Fair Value, Inputs, Level 1 [Member]
Cash equivalents	26,005,000	4,136,000
Equity securities	21,808,000	16,344,000
Available-for-sale fixed income securities	27,167,000	47,361,000
Investments, Fair Value Disclosure	74,980,000	67,841,000
Fair Value, Inputs, Level 2 [Member]
Cash equivalents	0	0
Equity securities	0	0
Available-for-sale fixed income securities	0	250,000
Investments, Fair Value Disclosure	0	250,000
Fair Value, Inputs, Level 3 [Member]
Cash equivalents	0	0
Equity securities	0	0
Available-for-sale fixed income securities	0	0
Investments, Fair Value Disclosure	$ 0	$ 0