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	Jun. 30, 2015	Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	$ 50,075	$ 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		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		5,545
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		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		1,550
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	50,075	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		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		5,545
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		2,369
Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Total assets measured at fair value	50,075	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	$ 50,075	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		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		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		1,830
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		$ 1,830