Summary of Cash and Cash Equivalents (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2015	Apr. 30, 2014
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	$ 45,787	$ 31,934
Demand deposits accounts
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	43,006	24,721
Money Market Funds
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	1,100	6,971
Certificates of Deposit
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents		242
Commercial Paper
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	1,280
Corporate Bonds
Cash and Cash Equivalents [Line Items]
Total cash and cash equivalents	$ 401