Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Revenues
Total revenues	$ 6,906.9	$ 6,987.5	$ 13,882.3	$ 12,761.3
Retail automotive dealership
Revenues
Total revenues	5,997.3	6,197.6	12,026.5	11,404.5	$ 22,500.0
Retail automotive dealership | U.S.
Revenues
Total revenues	3,443.9	3,614.5	6,787.5	6,619.3
Retail automotive dealership | U.K.
Revenues
Total revenues	2,196.4	2,190.6	4,459.3	4,044.0
Retail automotive dealership | Germany, Italy, and Japan
Revenues
Total revenues	357.0	392.5	779.7	741.2
Retail commercial truck dealership
Revenues
Total revenues	768.7	625.3	1,561.0	1,060.0
New vehicle | Retail automotive dealership
Revenues
Total revenues	2,446.0	2,811.3	4,891.5	5,232.7
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,387.8	2,327.6	4,810.7	4,135.6
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	221.4	212.3	438.7	381.1
Finance and insurance, net | Retail commercial truck dealership
Revenues
Total revenues	4.5	3.8	10.9	6.9
Service and parts | Retail automotive dealership
Revenues
Total revenues	597.0	546.2	1,183.2	1,049.4
Service and parts | Retail commercial truck dealership
Revenues
Total revenues	219.6	157.3	416.6	281.9
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 345.1	$ 300.2	$ 702.4	$ 605.7