Deferred Tax Amounts (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2013	Apr. 30, 2012
Income Taxes [Line Items]
Current, Deferred tax assets	$ 12,561	$ 15,868
Current, Deferred tax liabilities	(9,050)	(5,038)
Current deferred tax asset, net	3,511	10,830
Non-current, Deferred tax asset	117,199	96,966
Non-current, Deferred tax liabilities	(26,265)	(14,587)
Valuation allowance	(27,731)	(25,089)
Non-current deferred tax asset, net	63,203	57,290
Net deferred tax asset	$ 66,714	$ 68,120