Segment Information - Total Assets, Equity Method Investments, and Capital Expenditures by Reporting Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Total assets	$ 14,114.6	$ 13,464.6
Equity method investments	1,636.9	1,688.1
Capital expenditures	282.5	248.9	$ 185.9
Operating segments | Retail automotive dealership
Segment Reporting Information [Line Items]
Total assets	10,483.3	9,940.4
Equity method investments	41.1	40.7
Capital expenditures	245.6	239.4	175.6
Operating segments | Retail commercial truck dealership
Segment Reporting Information [Line Items]
Total assets	1,471.9	1,269.4
Equity method investments	0.0	0.0
Capital expenditures	31.2	6.3	7.2
Operating segments | Other
Segment Reporting Information [Line Items]
Total assets	563.6	607.4
Equity method investments	0.0	0.0
Capital expenditures	5.7	3.2	3.1
Operating segments | Non-Automotive Investments
Segment Reporting Information [Line Items]
Total assets	1,595.8	1,647.4
Equity method investments	1,595.8	1,647.4
Capital expenditures	$ 0.0	$ 0.0	$ 0.0