Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Assets and Liabilities Measured at Fair Value on a Recurring Basis, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	$ 52,455	$ 48,369
Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value		718
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	52,455	47,651
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Cash Equivalents
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	9,802	5,101
Cash Equivalents | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Cash Equivalents | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	9,802	5,101
Cash Equivalents | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | U.S. government and government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	34,377	28,854
Available-for-sale debt securities | Mortgage-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	2,601	2,999
Available-for-sale debt securities | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	3,447	3,213
Available-for-sale debt securities | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	532	598
Available-for-sale debt securities | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,696	6,886
Available-for-sale debt securities | Quoted Prices in Active Markets for Identical Instruments (Level 1) | U.S. government and government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Mortgage-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Quoted Prices in Active Markets for Identical Instruments (Level 1) | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2) | U.S. government and government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	34,377	28,854
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2) | Mortgage-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	2,601	2,999
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2) | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	3,447	3,213
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2) | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	532	598
Available-for-sale debt securities | Significant Other Observable Inputs (Level 2) | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,696	6,886
Available-for-sale debt securities | Significant Unobservable Inputs (Level 3) | U.S. government and government agency obligations
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Significant Unobservable Inputs (Level 3) | Mortgage-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Significant Unobservable Inputs (Level 3) | Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Significant Unobservable Inputs (Level 3) | Asset-backed Securities
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Available-for-sale debt securities | Significant Unobservable Inputs (Level 3) | Corporate Bonds
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value
Other
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value		718
Other | Quoted Prices in Active Markets for Identical Instruments (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value		718
Other | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value