Organization and Summary of Significant Accounting Policies - Impairment Testing (Details) $ in Millions	12 Months Ended
	Dec. 31, 2024 USD ($) segment	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments	4
Goodwill | $	$ 2,371.3	$ 2,234.9	$ 2,154.7
Retail automotive dealership
Segment Reporting Information [Line Items]
Number of reportable segments	1
Number of operating segments	2
Number of reporting units	2
Goodwill | $	$ 1,803.8	$ 1,664.0	$ 1,617.6
Retail commercial truck dealership
Segment Reporting Information [Line Items]
Number of operating segments	1
Number of reporting units	1
Non-Automotive Investments
Segment Reporting Information [Line Items]
Goodwill | $	$ 0.0