Goodwill and Acquired Intangible Assets - Schedule of Aggregate Amortization Expense for Intangible Assets with Finite Lives (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of acquired intangible assets	$ 45,948	$ 42,018	$ 40,022
Cost of revenue	32,828	38,495	35,694
Total amortization expense	$ 78,776	$ 80,513	$ 75,716