Leases - Supplemental Cash Flow and Other Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2021
Cash received for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 48,391	$ 0	$ 0
Right-of-use assets obtained in exchange for amended operating lease liabilities	17,071	0	0
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	$ 5,204	$ 4,500	$ 3,100
Weighted-average remaining lease term (in years)	13 years 6 months	7 years	8 years
Weighted-average discount rate	8.00%	8.50%	8.50%