Stock-Based Compensation (Stock-Based Compensation Expense Allocated) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 3,509	$ 3,413	$ 3,995
Cost Of Sales And Distribution [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	606	531	735
Selling And Marketing Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	859	715	842
General And Administrative Expense [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,044	$ 2,167	$ 2,418