Income Taxes - Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2018	Apr. 30, 2017
Income Tax Disclosure [Abstract]
Balance at beginning of the period	$ 33	$ 54
Decreases as a result of positions taken during prior periods	(1)	(25)
Increases as a result of positions taken during the current period		4
Balance at April 30,	$ 32	$ 33