Summary of Accrued Expenses (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013
Accrued Expenses [Line Items]
Accrued rebates and promotions	$ 2,633	$ 3,900
Accrued professional fees	2,374	2,882
Interest payable	2,194	1,542
Accrued employee benefits	2,148	1,953
Accrued settlement charges	2,000
Accrued workers' compensation	916	963
Accrued commissions	596	949
Accrued distributor incentives	590	458
Accrued utilities	532	537
Current portion of capital lease obligation	469	442
Accrued other	1,599	2,407
Total accrued expenses	$ 16,051	$ 16,033