Leases - Components of Lease Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Lease Cost
Operating lease cost	$ 32,402	$ 34,346	$ 37,295
Short-term lease cost	5,411	2,653	2,452
Variable lease cost	10,945	10,095	9,808
Sublease income	(4,749)	(4,600)	(4,438)
Total lease cost	$ 44,009	$ 42,494	$ 45,117