Computations of Loss per Share Applicable to Common Stockholders (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Jan. 31, 2015		Jan. 31, 2014		Jan. 31, 2015		Jan. 31, 2014
Schedule Of Computation Of Basic And Diluted Earnings Per Common Share [Line Items]
Net loss from continuing operations	$ (4,123)		$ (8,393)		$ (24,339)		$ (40,613)
Net income (loss) from discontinued operations, net of tax			430		(1,257)		1,128
Net loss applicable to common stockholders	$ (4,123)		$ (7,963)		$ (25,596)		$ (39,485)
Continuing operations	$ (0.05)		$ (0.11)		$ (0.31)		$ (0.54)
Discontinued operations			$ 0.01		$ (0.02)		$ 0.02
Basic and diluted loss per share	$ (0.05)		$ (0.10)		$ (0.33)		$ (0.52)	[1]
Basic and diluted weighted average number of shares outstanding	78,898		76,071		78,315		75,047
Outstanding stock options
Potentially dilutive securities (1):
Outstanding stock options	721	[2]	1,761	[2]	817	[2]	2,520	[2]
Restricted Stock
Potentially dilutive securities (1):
Outstanding stock options	629	[2]	219	[2]	404	[2]	271	[2]

[1] The sum of the earnings per share amounts for continuing and discontinued operations does not equal the total earnings per share amount for the year as previously reported due to the effects of rounding.

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