Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Income Tax Disclosure [Abstract]
Income taxes at the statutory rates	30.40%	35.00%	35.00%
Change in tax rate provisional income tax expense (benefit)	$ 173,000
Operating Loss Carryforwards [Line Items]
Valuation allowance	47	$ 60
Valuation allowance, increase (decrease)	(13)	(24)
Unrecognized tax benefits	6,421	5,362	$ 6,484
Unrecognized tax benefits that would impact effective tax rate	5,095
Increase (decrease) in unrecognized tax benefits	1,059
Accrued interest and penalties	191	141
Increase in tax expense	50	$ (76)
Decrease in unrecognized tax benefits is reasonable possible	1,300
Federal
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	13,188
State
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	82,243
Tax credit carryforward	$ 380