Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Revenues
Total revenues	$ 7,662.3	$ 7,696.7	$ 15,266.8	$ 15,144.5
Retail automotive dealership
Revenues
Total revenues	6,517.5	6,615.4	13,086.8	13,093.4
Retail automotive dealership | U.S.
Revenues
Total revenues	3,795.1	3,712.7	7,486.1	7,127.7
Retail automotive dealership | U.K.
Revenues
Total revenues	2,085.8	2,399.0	4,409.0	4,945.5
Retail automotive dealership | Germany, Italy, Japan, and Australia
Revenues
Total revenues	636.6	503.7	1,191.7	1,020.2
New vehicle | Retail automotive dealership
Revenues
Total revenues	2,941.8	2,995.8	5,963.9	5,798.4
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,200.5	2,275.8	4,401.0	4,612.0
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	200.5	208.7	398.7	414.7
Service and parts | Retail automotive dealership
Revenues
Total revenues	816.6	752.8	1,606.0	1,498.9
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 358.1	$ 382.3	$ 717.2	$ 769.4