Employee Stock Plans - Components of Stock-Based Compensation Expense Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2019	Jul. 31, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5,462	$ 5,714
Restricted Stock
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	5,091	5,369
ESPP
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 371	$ 345