Investments - Summary of Fair Value of Investments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Sep. 30, 2019
Assets
Short-term investments	$ 18,271	$ 16,502
Total assets at fair value	25,076	18,054
Liabilities
Acquisition-related contingent consideration	1,642	1,601
Total liabilities at fair value	1,642	1,601
U.S. Treasury
Assets
Short-term investments	5,219	4,242
Long-term investments	4,034	1,101
Asset-backed securities
Assets
Short-term investments	801
Long-term investments	2,117
Corporate debt securities | Financial
Assets
Short-term investments	2,954	2,503
Long-term investments	654	451
Corporate debt securities | Industrial
Assets
Short-term investments	1,372	1,371
Commercial paper | Financial
Assets
Short-term investments	5,334	5,560
Commercial paper | Industrial
Assets
Short-term investments	2,591	2,826
Quoted Prices in Active Markets (Level 1)
Assets
Short-term investments	5,219	4,242
Total assets at fair value	9,253	5,343
Liabilities
Acquisition-related contingent consideration	0	0
Total liabilities at fair value	0	0
Quoted Prices in Active Markets (Level 1) | U.S. Treasury
Assets
Short-term investments	5,219	4,242
Long-term investments	4,034	1,101
Quoted Prices in Active Markets (Level 1) | Asset-backed securities
Assets
Short-term investments	0
Long-term investments	0
Quoted Prices in Active Markets (Level 1) | Corporate debt securities | Financial
Assets
Short-term investments	0	0
Long-term investments	0	0
Quoted Prices in Active Markets (Level 1) | Corporate debt securities | Industrial
Assets
Short-term investments	0	0
Quoted Prices in Active Markets (Level 1) | Commercial paper | Financial
Assets
Short-term investments	0	0
Quoted Prices in Active Markets (Level 1) | Commercial paper | Industrial
Assets
Short-term investments	0	0
Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	13,052	12,260
Total assets at fair value	15,823	12,711
Liabilities
Acquisition-related contingent consideration	0	0
Total liabilities at fair value	0	0
Significant Other Observable Inputs (Level 2) | U.S. Treasury
Assets
Short-term investments	0	0
Long-term investments	0	0
Significant Other Observable Inputs (Level 2) | Asset-backed securities
Assets
Short-term investments	801
Long-term investments	2,117
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Financial
Assets
Short-term investments	2,954	2,503
Long-term investments	654	451
Significant Other Observable Inputs (Level 2) | Corporate debt securities | Industrial
Assets
Short-term investments	1,372	1,371
Significant Other Observable Inputs (Level 2) | Commercial paper | Financial
Assets
Short-term investments	5,334	5,560
Significant Other Observable Inputs (Level 2) | Commercial paper | Industrial
Assets
Short-term investments	2,591	2,826
Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0	0
Total assets at fair value	0	0
Liabilities
Acquisition-related contingent consideration	1,642	1,601
Total liabilities at fair value	1,642	1,601
Significant Unobservable Inputs (Level 3) | U.S. Treasury
Assets
Short-term investments	0	0
Long-term investments	0	0
Significant Unobservable Inputs (Level 3) | Asset-backed securities
Assets
Short-term investments	0
Long-term investments	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Financial
Assets
Short-term investments	0	0
Long-term investments	0	0
Significant Unobservable Inputs (Level 3) | Corporate debt securities | Industrial
Assets
Short-term investments	0	0
Significant Unobservable Inputs (Level 3) | Commercial paper | Financial
Assets
Short-term investments	0	0
Significant Unobservable Inputs (Level 3) | Commercial paper | Industrial
Assets
Short-term investments	$ 0	$ 0