Schedule II Valuation and Qualifying Accounts (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Apr. 30, 2011
Allowance for doubtful accounts, customer and other
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 788	$ 381	$ 228
Additions	3,042	1,083	482
Deductions	(1,162)	(676)	(329)
Ending Balance	2,668	788	381
Valuation allowance for deferred tax assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	19,854	12,391	6,209
Additions	20,588	7,463	6,182
Deductions	(2,540)
Ending Balance	$ 37,902	$ 19,854	$ 12,391