Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Revenues
Total revenues	$ 7,447.8	$ 7,339.0
Retail automotive dealership
Revenues
Total revenues	6,478.0	6,299.8
Retail automotive dealership | U.S.
Revenues
Total revenues	3,415.0	3,378.2
Retail automotive dealership | U.K.
Revenues
Total revenues	2,546.5	2,472.4
Retail automotive dealership | Germany, Italy, and Japan
Revenues
Total revenues	516.5	449.2
New vehicle | Retail automotive dealership
Revenues
Total revenues	2,802.6	2,721.3
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,336.2	2,297.1
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	206.0	206.8
Service and parts | Retail automotive dealership
Revenues
Total revenues	746.1	683.0
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 387.1	$ 391.6