Intangible Assets - Narrative (Details) - USD ($)	Sep. 30, 2024	Dec. 31, 2023
Goodwill [Line Items]
Goodwill	$ 2,405,700,000	$ 2,234,900,000
Retail automotive dealership
Goodwill [Line Items]
Goodwill	1,822,200,000
Retail commercial truck dealership
Goodwill [Line Items]
Goodwill	505,700,000
Other
Goodwill [Line Items]
Goodwill	77,800,000
Non-Automotive Investments
Goodwill [Line Items]
Goodwill	$ 0