Fair Value Measurements - Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (Assets and Liabilities Measured at Fair Value on a Recurring Basis [Member], USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	$ 45,606	$ 59,963
U.S. government and government agency obligations [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	9,519	7,394
Mortgage-backed securities [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	5,142	5,545
Asset-backed securities [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,946	2,369
Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	8,651	1,550
Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member] | U.S. government and government agency obligations [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	8,651
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	36,955	58,413
Significant Other Observable Inputs (Level 2) [Member] | U.S. government and government agency obligations [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	868	7,394
Significant Other Observable Inputs (Level 2) [Member] | Mortgage-backed securities [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	5,142	5,545
Significant Other Observable Inputs (Level 2) [Member] | Asset-backed securities [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,946	2,369
Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	26,487	40,100
Cash equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	26,487	40,100
Available-for-sale equity securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value		1,550
Available-for-sale equity securities [Member] | Quoted Prices in Active Markets for Identical Instruments (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value		1,550
Municipal bonds [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	785	1,175
Municipal bonds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	785	1,175
Corporate bonds [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	1,727	1,830
Corporate bonds [Member] | Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale debt securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	$ 1,727	$ 1,830