Summary of Significant Accounting Policies - Revenue Recognition (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2023
Contract with Customer, Liability [Roll Forward]
Beginning contract liability	$ 63,955	$ 51,649	$ 65,460
Revenue recognized from contract liabilities included in the beginning balance	(63,375)	(48,642)	(63,207)
Increases due to business combinations and cash received, net of amounts recognized in revenue during the period	28,700	60,948	49,396
Ending contract liability	29,280	63,955	$ 51,649
Allowance for credit loss, current	$ 4,600	$ 4,200