v2.4.0.8
Summary of Fair Value of Financial Assets and Liabilities (Detail) (USD $)
In Thousands, unless otherwise specified
Oct. 31, 2014
Apr. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents $ 32,855 $ 31,934
Short-term investments 48,639 40,700
Fair Value, Measurements, Recurring
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 4,252 7,213
Restricted cash 1,000 604
Short-term investments 48,639 40,700
Total assets 53,891 48,517
Fair Value, Measurements, Recurring | Certificates of Deposit
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents   242
Short-term investments 7,512 7,474
Fair Value, Measurements, Recurring | Municipal Bonds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 103  
Short-term investments 3,287  
Fair Value, Measurements, Recurring | Commercial Paper
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 5,999  
Fair Value, Measurements, Recurring | US Treasury notes
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 31,841 33,226
Fair Value, Measurements, Recurring | Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 4,149 6,971
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 4,149 7,213
Restricted cash 1,000 604
Short-term investments 31,841 33,226
Total assets 36,990 41,043
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Certificates of Deposit
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents   242
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | US Treasury notes
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 31,841 33,226
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 1 | Money Market Funds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 4,149 6,971
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 103  
Short-term investments 16,798 7,474
Total assets 16,901 7,474
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Certificates of Deposit
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments 7,512 7,474
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Municipal Bonds
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Cash equivalents 103  
Short-term investments 3,287  
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2 | Commercial Paper
    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Short-term investments $ 5,999