Goodwill and Intangible Assets - Narrative (Details) - USD ($)	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2022
Indefinite-Lived Intangible Assets [Line Items]
Impairment, intangible asset, indefinite-lived (excluding goodwill), extensible enumeration		Restructuring and impairment
Impairment, intangible asset, finite-lived (excluding goodwill), extensible enumeration		Restructuring and impairment
Restructuring and impairment	$ 539,000	$ 147,402,000	$ 0
Amortization expense	$ 7,842,000	13,436,000	7,600,000
Weighted average useful life	3 years 7 months 6 days
Goodwill	$ 336,602,000	336,602,000	378,588,000
Restructuring Costs and Asset Impairment Charges	15,318,000	147,402,000
2023 Impairment
Indefinite-Lived Intangible Assets [Line Items]
Restructuring Costs and Asset Impairment Charges	0	147,400,000	0
Domain Names
Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	637,000	528,000
Internally Developed Software
Indefinite-Lived Intangible Assets [Line Items]
Amortization expense	1,039,000	613,000	$ 100,000
Dealerships
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	295,300,000	295,300,000
Dealerships | 2023 Impairment
Indefinite-Lived Intangible Assets [Line Items]
Restructuring Costs and Asset Impairment Charges		6,500,000
Distribution
Indefinite-Lived Intangible Assets [Line Items]
Goodwill	$ 41,300,000	41,300,000
Distribution | 2023 Impairment
Indefinite-Lived Intangible Assets [Line Items]
Restructuring Costs and Asset Impairment Charges		$ 140,900,000