Investments - Summary of Fair Value of Investments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020
Assets
Total short-term investments at fair value	$ 149,057	$ 40,035
Total long-term investments at fair value	48,051	1,963
Convertible senior notes hedge	48,208
Total assets at fair value	245,316	41,998
Current liabilities:
Acquisition-related contingent consideration	11,050	753
Non-current liabilities:
Acquisition-related contingent consideration	5,720
Embedded conversion derivative	48,208
Total liabilities at fair value	64,978	753
U.S. Treasury
Assets
Total short-term investments at fair value	4,223	10,283
Total long-term investments at fair value	6,995
Asset-backed securities
Assets
Total short-term investments at fair value	4,811	4,759
Corporate debt securities
Assets
Total short-term investments at fair value	65,666	9,619
Total long-term investments at fair value	38,148	1,963
Commercial paper
Assets
Total short-term investments at fair value	74,357	15,374
Foreign government and agency securities
Assets
Total long-term investments at fair value	2,908
Quoted Prices in Active Markets (Level 1)
Assets
Total short-term investments at fair value	4,223	10,283
Total long-term investments at fair value	6,995	0
Convertible senior notes hedge	0
Total assets at fair value	11,218	10,283
Current liabilities:
Acquisition-related contingent consideration	0	0
Non-current liabilities:
Acquisition-related contingent consideration	0
Embedded conversion derivative	0
Total liabilities at fair value	0	0
Quoted Prices in Active Markets (Level 1) \| U.S. Treasury
Assets
Total short-term investments at fair value	4,223	10,283
Total long-term investments at fair value	6,995
Quoted Prices in Active Markets (Level 1) \| Asset-backed securities
Assets
Total short-term investments at fair value	0	0
Quoted Prices in Active Markets (Level 1) \| Corporate debt securities
Assets
Total short-term investments at fair value	0	0
Total long-term investments at fair value	0	0
Quoted Prices in Active Markets (Level 1) \| Commercial paper
Assets
Total short-term investments at fair value	0	0
Quoted Prices in Active Markets (Level 1) \| Foreign government and agency securities
Assets
Total long-term investments at fair value	0
Significant Other Observable Inputs (Level 2)
Assets
Total short-term investments at fair value	144,834	29,752
Total long-term investments at fair value	41,056	1,963
Convertible senior notes hedge	48,208
Total assets at fair value	234,098	31,715
Current liabilities:
Acquisition-related contingent consideration	0	0
Non-current liabilities:
Acquisition-related contingent consideration	0
Embedded conversion derivative	48,208
Total liabilities at fair value	48,208	0
Significant Other Observable Inputs (Level 2) \| U.S. Treasury
Assets
Total short-term investments at fair value	0	0
Total long-term investments at fair value	0
Significant Other Observable Inputs (Level 2) \| Asset-backed securities
Assets
Total short-term investments at fair value	4,811	4,759
Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Assets
Total short-term investments at fair value	65,666	9,619
Total long-term investments at fair value	38,148	1,963
Significant Other Observable Inputs (Level 2) \| Commercial paper
Assets
Total short-term investments at fair value	74,357	15,374
Significant Other Observable Inputs (Level 2) \| Foreign government and agency securities
Assets
Total long-term investments at fair value	2,908
Significant Unobservable Inputs (Level 3)
Assets
Total short-term investments at fair value	0	0
Total long-term investments at fair value	0	0
Convertible senior notes hedge	0
Total assets at fair value	0	0
Current liabilities:
Acquisition-related contingent consideration	11,050	753
Non-current liabilities:
Acquisition-related contingent consideration	5,720
Embedded conversion derivative	0
Total liabilities at fair value	16,770	753
Significant Unobservable Inputs (Level 3) \| U.S. Treasury
Assets
Total short-term investments at fair value	0	0
Total long-term investments at fair value	0
Significant Unobservable Inputs (Level 3) \| Asset-backed securities
Assets
Total short-term investments at fair value	0	0
Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Assets
Total short-term investments at fair value	0	0
Total long-term investments at fair value	0	0
Significant Unobservable Inputs (Level 3) \| Commercial paper
Assets
Total short-term investments at fair value	0	$ 0
Significant Unobservable Inputs (Level 3) \| Foreign government and agency securities
Assets
Total long-term investments at fair value	$ 0

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