Held to Maturity Investments Which are Not Recorded at Fair Value (Detail) (USD $)	Oct. 31, 2013	Apr. 30, 2013
Schedule of Held-to-maturity Securities [Line Items]
Carrying value	$ 0	$ 226,000
Unrealized Gain		1,000
Unrealized Loss
Fair value		227,000
Certificates of Deposit
Schedule of Held-to-maturity Securities [Line Items]
Carrying value
Unrealized Gain
Tax-exempt state and municipal bonds
Schedule of Held-to-maturity Securities [Line Items]
Carrying value		226,000
Unrealized Gain		1,000
Fair value		$ 227,000