Stock-Based Compensation (Stock-Based Compensation Expense Allocated) (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Oct. 31, 2018	Oct. 31, 2017	Jul. 31, 2017	Oct. 31, 2018	Oct. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 836		$ 664	$ 1,622	$ 1,609
Cost of Sales and Distribution [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	185	$ 277		344	521
Selling and Marketing Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	217	(44)		385	202
General and Administrative Expenses [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 434	$ 431		$ 893	$ 886