Business Acquisitions (Schedule of Unaudited Proforma Combined Financial Information) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Business Acquisition [Line Items]
Revenue	$ 116,291	$ 119,456	$ 366,089	$ 386,578
Operating income	40	4,753	10,748	27,306
Net loss attributable to common stockholders	$ (11,442)	$ (24,795)	$ (41,042)	$ (28,951)
Basic and diluted loss per common share attributable to common stockholders	$ (0.29)	$ (0.92)	$ (1.27)	$ (1.08)
Basic and diluted weighted average shares outstanding	39,230	26,822	32,365	26,715