Investments - Summary of Fair Value of Investments Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Sep. 30, 2021
Assets:
Short-term investments:	$ 49,531	$ 149,057
Long-term investments:	19,534	48,051
Convertible senior notes hedge		48,208
Total assets at fair value	69,065	245,316
Current liabilities:
Acquisition-related contingent consideration	4,980	11,050
Non-current liabilities:
Acquisition-related contingent consideration	100	5,720
Embedded conversion derivative		48,208
Total liabilities at fair value	5,080	64,978
U.S. Treasury
Assets:
Short-term investments:	3,953	4,223
Long-term investments:	5,228	6,995
Asset-backed securities
Assets:
Short-term investments:		4,811
Foreign government and agency securities
Assets:
Short-term investments:	2,832
Long-term investments:		2,908
Corporate debt securities
Assets:
Short-term investments:	42,746	140,023
Long-term investments:	14,306	38,148
Quoted Prices in Active Markets (Level 1)
Assets:
Short-term investments:	3,953	4,223
Long-term investments:	5,228	6,995
Convertible senior notes hedge		0
Total assets at fair value	9,181	11,218
Current liabilities:
Acquisition-related contingent consideration	0	0
Non-current liabilities:
Acquisition-related contingent consideration	0	0
Embedded conversion derivative		0
Total liabilities at fair value	0	0
Quoted Prices in Active Markets (Level 1) \| U.S. Treasury
Assets:
Short-term investments:	3,953	4,223
Long-term investments:	5,228	6,995
Quoted Prices in Active Markets (Level 1) \| Asset-backed securities
Assets:
Short-term investments:		0
Quoted Prices in Active Markets (Level 1) \| Foreign government and agency securities
Assets:
Short-term investments:	0
Long-term investments:		0
Quoted Prices in Active Markets (Level 1) \| Corporate debt securities
Assets:
Short-term investments:	0	0
Long-term investments:	0	0
Significant Other Observable Inputs (Level 2)
Assets:
Short-term investments:	45,578	144,834
Long-term investments:	14,306	41,056
Convertible senior notes hedge		48,208
Total assets at fair value	59,884	234,098
Current liabilities:
Acquisition-related contingent consideration	0	0
Non-current liabilities:
Acquisition-related contingent consideration	0	0
Embedded conversion derivative		48,208
Total liabilities at fair value	0	48,208
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:		4,811
Significant Other Observable Inputs (Level 2) \| Foreign government and agency securities
Assets:
Short-term investments:	2,832
Long-term investments:		2,908
Significant Other Observable Inputs (Level 2) \| Corporate debt securities
Assets:
Short-term investments:	42,746	140,023
Long-term investments:	14,306	38,148
Significant Unobservable Inputs (Level 3)
Assets:
Short-term investments:	0	0
Long-term investments:	0	0
Convertible senior notes hedge		0
Total assets at fair value	0	0
Current liabilities:
Acquisition-related contingent consideration	4,980	11,050
Non-current liabilities:
Acquisition-related contingent consideration	100	5,720
Embedded conversion derivative		0
Total liabilities at fair value	5,080	16,770
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
Significant Unobservable Inputs (Level 3) \| Foreign government and agency securities
Assets:
Short-term investments:	0
Long-term investments:		0
Significant Unobservable Inputs (Level 3) \| Corporate debt securities
Assets:
Short-term investments:	0	0
Long-term investments:	$ 0	$ 0

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