Note 4 - Supplementary Cash Flows Information - Supplementary Cash Flow Elements (Details) - USD ($)	9 Months Ended
	Jan. 31, 2022	Jan. 31, 2021	Apr. 30, 2021
Cash and cash equivalents	$ 29,909,000	$ 16,182,000	$ 19,171,000
Restricted cash	305,000	469,000
Total cash, cash equivalents, and restricted cash shown in the Consolidated Condensed Statement of Cash Flows	30,214,000	16,651,000
State and local income tax payments	544,000	1,139,000
Federal income tax payments to the Parent	$ 2,300,000	$ 5,210,000