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	Dec. 31, 2016	Sep. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	$ 41,249	$ 44,114
Liabilities measured at fair value	(14,291)	(14,517)
Available-for-sale securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	27,474	21,954
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	41,249	44,114
Significant Other Observable Inputs (Level 2) [Member] | Available-for-sale securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	27,474	21,954
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	(14,291)	(14,517)
Cash equivalents [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	13,775	22,160
Cash equivalents [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Assets measured at fair value	13,775	22,160
Contingent consideration [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	(14,291)	(14,517)
Contingent consideration [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]
Liabilities measured at fair value	$ (14,291)	$ (14,517)