Income Taxes Other (Details) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Unrecognized tax benefits
State net operating loss carryforwards	$ 10,000
Foreign net operating loss carryforwards	660,000
Foreign net operating losses subject to expiration	320,000
Activity related to gross unrecognized tax benefits
Beginning balance	12,593,000	$ 11,170,000
Increases related to prior year tax positions	62,000	216,000
Increases related to current year tax positions	1,971,000	1,756,000
Decreases related to lapsing of statute of limitations	(279,000)	(549,000)
Ending balance	14,347,000	12,593,000
Reversal of uncertain tax position reserve, including interest	279,000
Accrued interest and penalties related to unrecognized tax positions	21,000	$ 18,000
Statute of limitations expiration
Unrecognized tax benefits
Estimated decrease in unrecognized tax benefits in the next twelve months	$ (53,600)