v2.4.0.8
Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)
In Thousands, unless otherwise specified
Jun. 30, 2013
Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis $ 82,889 $ 93,002
Money market funds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 11,107 32,506
Corporate bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 16,844 18,215
Municipal bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 39,106 23,566
Certificates of deposit
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 7,569 14,209
Commercial Paper
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 8,263 4,506
Quoted Prices in Active Markets for Identical Assets (Level 1)
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 27,951 50,721
Quoted Prices in Active Markets for Identical Assets (Level 1) | Money market funds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 11,107 32,506
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 16,844 18,215
Quoted Prices in Active Markets for Identical Assets (Level 1) | Municipal bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Certificates of deposit
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 0 0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Commercial Paper
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 0 0
Significant Other Observable Inputs (Level 2)
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 54,938 42,281
Significant Other Observable Inputs (Level 2) | Money market funds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 0 0
Significant Other Observable Inputs (Level 2) | Corporate bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 0 0
Significant Other Observable Inputs (Level 2) | Municipal bonds
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 39,106 23,566
Significant Other Observable Inputs (Level 2) | Certificates of deposit
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis 7,569 14,209
Significant Other Observable Inputs (Level 2) | Commercial Paper
    
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]    
Total assets at fair value on a recurring basis $ 8,263 $ 4,506