Goodwill and Other Identifiable Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2022
Indefinite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 3,400	$ 2,100	$ 9,962	$ 4,700
Weighted average useful life			4 years 4 months 24 days
Goodwill	397,469		$ 397,469		$ 378,588
Domain Names
Indefinite-Lived Intangible Assets [Line Items]
Amortization of intangible assets			$ 359
Weighted average useful life			4 years 3 months 18 days
Internally Developed Software
Indefinite-Lived Intangible Assets [Line Items]
Amortization of intangible assets			$ 382
Weighted average useful life			4 years 6 months
Dealerships
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	298,500		$ 298,500		280,000
Distribution
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 99,000		$ 99,000		$ 98,600