Organization and Summary of Significant Accounting Policies - Impairment Testing (Details) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) segment	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments	4
Goodwill | $	$ 2,435.7	$ 2,376.3	$ 2,239.9
Retail automotive dealership
Segment Reporting Information [Line Items]
Number of reportable segments	1
Number of operating segments	2
Number of reporting units	2
Goodwill | $	$ 1,859.1	$ 1,808.8	$ 1,669.0
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