Summary of Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Apr. 30, 2014
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	$ 24,704	$ 31,934
Demand deposits accounts
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	21,674	24,721
Money Market Funds
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	1,442	6,971
Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents		242
Municipal Bonds
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	887
US Treasury securities
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	$ 701