Summary of Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2014	Apr. 30, 2013
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	$ 31,934	$ 25,045
Demand deposit accounts
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	24,721	16,522
Money Market Funds
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	6,971	1,314
Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	242
U.S. Treasury securities
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents		$ 7,209