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		9 Months Ended
		Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2016	Jan. 31, 2015
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net loss from continuing operations		$ (3,114)	$ (4,123)	$ (18,210)	$ (24,339)
Net loss from discontinued operations, net of tax		0	0	0	(1,257)
Net loss applicable to common stockholders		$ (3,114)	$ (4,123)	$ (18,210)	$ (25,596)
Continuing operations		$ (0.04)	$ (0.05)	$ (0.23)	$ (0.31)
Discontinued operations		0.00	0.00	0.00	(0.02)
Basic and diluted loss per share:		$ (0.04)	$ (0.05)	$ (0.23)	$ (0.33)
Basic and diluted weighted average number of shares outstanding		81,096	78,898	80,649	78,315
Outstanding stock options
Potentially dilutive securities (1):
Outstanding stock options	[1]	168	721	224	817
Restricted shares
Potentially dilutive securities (1):
Outstanding stock options	[1]	17	629	50	404

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