Income Taxes income Taxes (Change in Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Change in Unrecognized Tax Benefits
Balance at beginning of year	$ 2,305	$ 2,240
Additions based on tax positions related to the current year	115	65
Unrecognized Tax Benefits, Decrease Resulting from Prior Period Tax Positions	(929)	0
Balance at end of year	$ 1,491	$ 2,305