Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Mar. 31, 2024	Mar. 31, 2023	Sep. 30, 2023
Indefinite-Lived Intangible Assets [Line Items]
Amortization of intangible assets	$ 2,100	$ 3,300	$ 3,656	$ 6,600
Weighted average useful life			3 years 9 months 18 days
Goodwill	336,602		$ 336,602		$ 336,602
Dealerships
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	295,300		295,300		295,300
Distribution
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 41,300		$ 41,300		$ 41,300