Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2017	Apr. 30, 2016	Apr. 30, 2015
Current:
Federal	$ 5,643	$ 4,105	$ 2,506
State	676	665	501
Current Income Tax Expense (Benefit), Total	6,319	4,770	3,007
Deferred:
Federal	558	(299)	(697)
State	117	(13)	(36)
Deferred Income Tax Expense (Benefit), Net of Valuation Allowance, Total	675	(312)	(733)
Income tax expense	$ 6,994	$ 4,458	$ 2,274