Note 3 - Financed Lease Right-of-use - Adoption of ASU 2016-02 (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Increase in depreciation	$ 5,116	$ 1,846
Increase in interest expense	4,368	248
Decrease in net income for the year ended April 30, 2020	(4,234)	$ (3,853)
Accounting Standards Update 2016-02 [Member]
Increase in depreciation	2,833
Increase in interest expense	4,167
Decrease in rent expense	(5,150)
Decrease in net income for the year ended April 30, 2020	$ 1,850