Held to Maturity Investments Which are Not Recorded at Fair Value (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013
Schedule of Held-to-maturity Securities [Line Items]
Carrying value		$ 226
Unrealized Gain		1
Unrealized Loss
Fair value		227
Certificates of deposit
Schedule of Held-to-maturity Securities [Line Items]
Unrealized Loss
Tax-exempt state and municipal bonds
Schedule of Held-to-maturity Securities [Line Items]
Carrying value		226
Unrealized Gain		1
Unrealized Loss
Fair value		$ 227