Net Loss Per Share Applicable to Common Stockholders - Computations of Loss per Share Applicable to Common Stockholders (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
		Jul. 31, 2015	Jul. 31, 2014
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net loss from continuing operations		$ (10,244)	$ (10,308)
Net loss from discontinued operations, net of tax		0	(1,257)
Net loss applicable to common stockholders		$ (10,244)	$ (11,565)
Continuing operations		$ (0.13)	$ (0.13)
Discontinued operations		0.00	(0.02)
Basic and diluted loss per share:		$ (0.13)	$ (0.15)
Basic and diluted weighted average number of shares outstanding		80,174	77,766
Outstanding stock options
Potentially dilutive securities (1):
Outstanding stock options	[1]	324	922
Restricted shares
Potentially dilutive securities (1):
Outstanding stock options	[1]	58	170

[1] The impact of potentially dilutive securities on earnings per share is anti-dilutive in a period of net loss.