Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 47	$ 47
Valuation allowance, increase (decrease)	0	(13)
Unrecognized tax benefits	7,287	6,421	$ 5,362
Unrecognized tax benefits that would impact effective tax rate	5,780
Increase (decrease) in unrecognized tax benefits	866
Accrued interest and penalties	242	191
Increase in tax expense	51	$ 50
Decrease in unrecognized tax benefits is reasonable possible	1,100
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	84,330
Tax credit carryforward	$ 504