Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023
Operating lease cost:
Operating lease cost	$ 19,840	$ 18,023	$ 38,906	$ 35,518
Variable lease cost	4,643	4,028	8,858	7,880
Total operating lease cost	24,483	22,051	47,764	43,398
Financing lease cost:
Amortization of financing lease assets	164	55	315	74
Interest on financing lease liabilities	63	24	128	35
Total financing lease cost	227	79	443	109
Total lease cost	24,710	22,130	48,207	43,507
Sublease income	$ 600	$ 1,100	$ 1,700	$ 1,800
Weighted-average remaining lease term (years):
Operating leases	4 years 10 months 17 days	5 years 1 month 28 days	4 years 10 months 17 days	5 years 1 month 28 days
Financing leases	3 years 2 months 1 day	3 years 11 months 19 days	3 years 2 months 1 day	3 years 11 months 19 days
Weighted-average discount rate:
Operating leases	8.41%	8.42%	8.41%	8.42%
Financing leases	11.14%	11.14%	11.14%	11.14%