Investments - Summary of Fair Value of Investments Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Sep. 30, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		$ 26,815
Acquisition-related contingent consideration	$ 282	252
Total liabilities at fair value	282	252
Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		13,900
Quoted Prices in Active Markets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		12,915
Significant Unobservable Inputs (Level 3) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration	282	252
Total liabilities at fair value	282	252
Short-term investments [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	28,314	24,863
Short-term investments [Member] | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	5,176	4,445
Short-term investments [Member] | Corporate debt securities [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	3,450	3,963
Short-term investments [Member] | Commercial paper [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	2,696	697
Short-term investments [Member] | Commercial paper [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	4,089	2,843
Short-term investments [Member] | U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	12,903	12,915
Short-term investments [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	15,411	11,948
Short-term investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	5,176	4,445
Short-term investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	3,450	3,963
Short-term investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	2,696	697
Short-term investments [Member] | Significant Other Observable Inputs (Level 2) [Member] | Commercial paper [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	4,089	2,843
Short-term investments [Member] | Quoted Prices in Active Markets (Level 1) [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	12,903	12,915
Short-term investments [Member] | Quoted Prices in Active Markets (Level 1) [Member] | U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value	$ 12,903	12,915
Long-term [Member] | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		1,450
Long-term [Member] | Corporate debt securities [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		502
Long-term [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		1,450
Long-term [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate debt securities [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets at fair value		$ 502