Schedule II Valuation and Qualifying Accounts (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Allowance for doubtful accounts, customer and other
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	$ 2,324	$ 2,371	$ 788
Additions	4,120	2,626	2,290
Deductions	(2,452)	(2,673)	(707)
Ending Balance	3,992	2,324	2,371
Valuation allowance for deferred tax assets
Valuation and Qualifying Accounts Disclosure [Line Items]
Beginning Balance	52,734	37,902	19,854
Additions	13,714	16,223	20,588
Deductions		(1,391)	(2,540)
Ending Balance	$ 66,448	$ 52,734	$ 37,902