Investments - Summary of Fair Value of Investments Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Sep. 30, 2015
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	$ 28,221	$ 23,921
Significant Unobservable Inputs (Level 3)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Acquisition-related contingent consideration	267	47
Total liabilities at fair value	267	47
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	3,569	9,665
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Corporate debt securities [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	5,422	10,308
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Corporate debt securities [Member] | Utility [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total		1,802
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Commercial paper [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total		1,448
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Commercial paper [Member] | Financial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	3,251	$ 698
Short-term [Member] | Significant Other Observable Inputs (Level 2) | Government debt securities [Member] | U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	7,666
Long-term [Member] | Significant Other Observable Inputs (Level 2) | Corporate debt securities [Member] | Industrial [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	2,298
Long-term [Member] | Significant Other Observable Inputs (Level 2) | Government debt securities [Member] | U.S. Treasury [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of investments measured on recurring basis, total	$ 6,015