Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Revenues
Total revenues	$ 6,920.7	$ 6,497.3	$ 20,803.0	$ 19,258.6
Retail automotive dealership
Revenues
Total revenues	5,757.8	5,634.9	17,784.3	17,039.4	$ 22,500.0
Retail automotive dealership | U.S.
Revenues
Total revenues	3,400.8	3,271.2	10,188.3	9,890.5
Retail automotive dealership | U.K.
Revenues
Total revenues	2,002.0	2,055.2	6,461.3	6,099.2
Retail automotive dealership | Germany, Italy, and Japan
Revenues
Total revenues	355.0	308.5	1,134.7	1,049.7
Retail commercial truck dealership
Revenues
Total revenues	1,019.5	717.3	2,580.5	1,777.3
New vehicle | Retail automotive dealership
Revenues
Total revenues	2,395.2	2,275.2	7,286.7	7,507.9
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,208.8	2,302.3	7,019.5	6,437.9
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	208.1	202.7	646.8	583.8
Finance and insurance, net | Retail commercial truck dealership
Revenues
Total revenues	5.5	4.8	16.4	11.7
Service and parts | Retail automotive dealership
Revenues
Total revenues	609.8	555.3	1,793.0	1,604.7
Service and parts | Retail commercial truck dealership
Revenues
Total revenues	223.9	160.9	640.5	442.8
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 335.9	$ 299.4	$ 1,038.3	$ 905.1