Earnings Per Share (Schedule of Numerator and Denominator Used In Computation of Basic and Diluted Earnings Per Share) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013 Class A Common Stock [Member]	Apr. 30, 2012 Class A Common Stock [Member]	Jan. 31, 2012 Class A Common Stock [Member]	Jan. 31, 2013 Class B Common Stock [Member]	Apr. 30, 2012 Class B Common Stock [Member]	Jan. 31, 2012 Class B Common Stock [Member]
Earnings Per Share [Line Items]
Loss from continuing operations before discontinued operations attributable to common stockholders	$ (11,407)	$ (24,635)	$ (40,747)	$ (29,186)
Common stock, shares outstanding					38,658,000	25,991,000	25,987,000	988,000	988,000	988,000
Unvested restricted stock	(134,000)	(127,000)	(134,000)	(127,000)
Effect of weighted average shares outstanding during period	(282,000)	(26,000)	(7,147,000)	(133,000)
Weighted average number of common shares used in basic and diluted EPS	39,230,000	26,822,000	32,365,000	26,715,000