Note 2 - Supplementary Cash Flow Information - Supplementary Cash Flow Elements (Details) - USD ($)	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
State and local income tax payments	$ 387,000	$ 307,000	$ 560,000
Federal income tax payments to the Parent	$ 2,700,000	$ 3,975,000	$ 6,824,000