Fair Value Measurements Narrative (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Sep. 30, 2013
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	$ 128,207	$ 90,391
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	128,207	90,391
Cash and Cash Equivalents, Fair Value Disclosure	30,433	7,754
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	2,199
Cash and Cash Equivalents, Fair Value Disclosure	2,045	6,152
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	128,207	88,192
Cash and Cash Equivalents, Fair Value Disclosure	$ 28,388	$ 1,602