Fair Value Measurements Narrative (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Sep. 30, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	$ 134,959	$ 151,342
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	134,959	151,342
Cash and Cash Equivalents, Fair Value Disclosure	8,893	6,404
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	0	0
Cash and Cash Equivalents, Fair Value Disclosure	8,145	5,166
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	134,959	151,342
Cash and Cash Equivalents, Fair Value Disclosure	$ 748	$ 1,238