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		6 Months Ended
		Oct. 31, 2015	Oct. 31, 2014	Oct. 31, 2015	Oct. 31, 2014
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net loss from continuing operations		$ (4,852)	$ (9,908)	$ (15,096)	$ (20,216)
Net loss from discontinued operations, net of tax		0	0	0	(1,257)
Net loss applicable to common stockholders		$ (4,852)	$ (9,908)	$ (15,096)	$ (21,473)
Continuing operations		$ (0.06)	$ (0.13)	$ (0.19)	$ (0.26)
Discontinued operations		0.00	0.00	0.00	(0.02)
Basic and diluted loss per share:		$ (0.06)	$ (0.13)	$ (0.19)	$ (0.28)
Basic and diluted weighted average number of shares outstanding		80,678	78,280	80,426	78,023
Outstanding stock options
Potentially dilutive securities (1):
Outstanding stock options	[1]	212	813	266	864
Restricted shares
Potentially dilutive securities (1):
Outstanding stock options	[1]	11	301	38	243

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