Stock-Based Compensation (Stock-Based Compensation Expense Allocated) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2020	Jan. 31, 2019
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 1,047	$ 668	$ 3,122	$ 2,290
Cost of Sales and Distribution [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	224	158	716	502
Selling and Marketing Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	240	64	713	449
General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 583	$ 446	$ 1,693	$ 1,339