Changes in Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Income Taxes [Line Items]
Unrecognized tax benefits, beginning of year	$ 2,423	$ 2,701	$ 3,400
Settlement with tax authority	(1,963)	(497)	(1,946)
Additions based on tax positions related to the current year	1,305	219	279
Additions based on tax positions related to prior years	330		968
Unrecognized tax benefits, end of year	$ 2,095	$ 2,423	$ 2,701