Income Taxes - Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017	Apr. 30, 2016
Current:
Federal	$ 2,298	$ 5,643	$ 4,105
State	743	676	665
Current Income Tax Expense (Benefit), Total	3,041	6,319	4,770
Deferred:
Federal	321	558	(299)
State	300	117	(13)
Deferred Federal, State and Local, Tax Expense (Benefit), Total	621	675	(312)
Income tax expense	$ 3,662	$ 6,994	$ 4,458