Leases - Lease Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 31, 2023	Mar. 31, 2022
Operating lease cost:
Operating lease cost	$ 18,023	$ 16,789	$ 35,518	$ 33,151
Variable lease cost	4,028	3,834	7,880	7,376
Total operating lease cost	22,051	20,623	43,398	40,527
Financing lease cost:
Amortization of financing lease assets	55	0	74	0
Interest on financing lease liabilities	24	0	35	0
Total financing lease cost	79	0	109	0
Total lease cost	22,130	20,623	43,507	40,527
Sublease income	$ 1,100	$ 800	$ 1,800	$ 1,700
Weighted-average remaining lease term (years):
Weighted-average remaining lease term, Operating leases (in years)	5 years 1 month 28 days	5 years	5 years 1 month 28 days	5 years
Weighted-average remaining lease term, Financing leases (in years)	3 years 11 months 19 days		3 years 11 months 19 days
Weighted-average discount rate:
Weighted-average discount rate, Operating leases (as percentage)	8.42%	8.27%	8.42%	8.27%
Weighted-average discount rate, Financing leases (as percentage)	11.14%		11.14%