Fair Value Measurements Narrative (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	$ 140,936	$ 151,342
Fair Value, Measurements, Recurring
Fair Value Assets And Liabilities Measured On Recurring Basis [Line Items]
Available-for-sale securities	140,936	151,342
Cash and Cash Equivalents, Fair Value Disclosure	2,848	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	1,950	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	140,936	151,342
Cash and Cash Equivalents, Fair Value Disclosure	$ 898	$ 1,238