Segment Information - Segment Reporting Information, by Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenues	[1]	$ 376,572	$ 312,974	$ 245,109
Cost of revenues		185,570	179,625	155,380
Depreciation and amortization expense		24,853	31,432	29,310
Total stock-based compensation expense		64,459	50,925	30,278
Restructuring and other costs		0	0	9,384
Change in fair value of contingent considerations and holdbacks		0	0	(5,913)
Impairment of long-lived assets		0	44,930	6,785
Total costs and expenses		512,831	533,805	462,268
Loss from operations		(136,259)	(220,831)	(217,159)
Gain on sale of business		48,847	0	0
Interest income		11,364	15,344	14,365
Other income (expense), net	[2]	(903)	(2,679)	(672)
Loss before income taxes		(76,951)	(208,166)	(203,466)
Income tax expense		(719)	(560)	(1,152)
Net loss attributable to common stockholders		(77,670)	(208,726)	(204,618)
Reportable Segment
Segment Reporting Information [Line Items]
Revenues		376,572	312,974	245,109
Cost of revenues		161,545	154,030	132,417
Research and development expenses		69,950	76,605	88,937
Selling, general and administrative expenses		192,024	175,883	171,070
Depreciation and amortization expense		24,853	31,432	29,310
Total stock-based compensation expense		64,459	50,925	30,278
Restructuring and other costs		0	0	9,384
Change in fair value of contingent considerations and holdbacks		0	0	(5,913)
Impairment of long-lived assets		0	44,930	6,785
Total costs and expenses		512,831	533,805	462,268
Loss from operations		(136,259)	(220,831)	(217,159)
Gain on sale of business		48,847	0	0
Interest income		11,364	15,344	14,365
Other income (expense), net		(903)	(2,679)	(672)
Loss before income taxes		(76,951)	(208,166)	(203,466)
Income tax expense		(719)	(560)	(1,152)
Net loss attributable to common stockholders		$ (77,670)	$ (208,726)	$ (204,618)

[1] Including revenues from related parties of $12.2 million, $12.1 million and $5.9 million during the year end September 30, 2025, 2024 and 2023, respectively.

[2] Including sublease income from a related party of $1.1 million, $— million and $— million during the year end September 30, 2025, 2024 and 2023, respectively.