Segment Information - Revenues and Segment Income by Reportable Segment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Segment Reporting Information [Line Items]
Revenues	$ 27,814.8	$ 25,554.7	$ 20,443.9
Floor plan interest expense	52.4	26.2	46.3
Other interest expense	70.4	68.6	111.0
Depreciation	127.3	121.5	115.5
Equity in earnings of affiliates	494.2	374.5	169.0
Income from continuing operations before income taxes	1,859.2	1,607.7	707.6
Retail automotive dealership
Segment Reporting Information [Line Items]
Revenues	23,694.7	22,513.3	17,928.8
Retail commercial truck dealership
Segment Reporting Information [Line Items]
Revenues	3,541.3	2,465.7	2,060.9
Operating segments | Retail automotive dealership
Segment Reporting Information [Line Items]
Revenues	23,694.7	22,513.3	17,928.8
Floor plan interest expense	44.5	23.9	39.6
Other interest expense	65.1	63.8	105.9
Depreciation	112.7	108.7	103.8
Equity in earnings of affiliates	3.5	8.2	4.4
Income from continuing operations before income taxes	1,118.0	1,046.6	443.4
Operating segments | Retail commercial truck dealership
Segment Reporting Information [Line Items]
Revenues	3,541.3	2,465.7	2,060.9
Floor plan interest expense	7.5	1.9	5.6
Other interest expense	3.9	3.3	3.7
Depreciation	10.0	7.9	6.4
Equity in earnings of affiliates	0.0	0.0	0.0
Income from continuing operations before income taxes	214.7	160.3	78.2
Operating segments | Other
Segment Reporting Information [Line Items]
Revenues	578.8	575.7	454.2
Floor plan interest expense	0.4	0.4	1.1
Other interest expense	1.4	1.5	1.4
Depreciation	4.6	4.9	5.3
Equity in earnings of affiliates	0.0	0.0	0.0
Income from continuing operations before income taxes	35.8	34.5	21.4
Operating segments | Non-Automotive Investments
Segment Reporting Information [Line Items]
Revenues	0.0	0.0	0.0
Floor plan interest expense	0.0	0.0	0.0
Other interest expense	0.0	0.0	0.0
Depreciation	0.0	0.0	0.0
Equity in earnings of affiliates	490.7	366.3	164.6
Income from continuing operations before income taxes	$ 490.7	$ 366.3	$ 164.6