Intangible Assets - Information by Segment (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Goodwill [Line Items]
Goodwill	$ 2,246.1	$ 2,154.7
Retail automotive dealership
Goodwill [Line Items]
Goodwill	1,681.5
Retail commercial truck dealership
Goodwill [Line Items]
Goodwill	492.0
Other
Goodwill [Line Items]
Goodwill	72.6
Non-Automotive Investments
Goodwill [Line Items]
Goodwill	$ 0.0