Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Revenues
Total revenues	$ 7,604.5	$ 7,447.8
Retail automotive dealership
Revenues
Total revenues	6,569.3	6,478.0
Retail automotive dealership | U.S.
Revenues
Total revenues	3,691.0	3,415.0
Retail automotive dealership | U.K.
Revenues
Total revenues	2,323.2	2,546.5
Retail automotive dealership | Germany, Italy, Japan, and Australia
Revenues
Total revenues	555.1	516.5
New vehicle | Retail automotive dealership
Revenues
Total revenues	3,022.1	2,802.6
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,200.5	2,336.2
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	198.2	206.0
Service and parts | Retail automotive dealership
Revenues
Total revenues	789.4	746.1
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 359.1	$ 387.1