Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Revenues
Total revenues	$ 30,455.2	$ 29,527.4	$ 27,814.8
U.S.
Revenues
Total revenues	17,715.1	17,186.5	16,801.7
U.K.
Revenues
Total revenues	9,322.0	9,240.4	8,443.4
Retail automotive dealership
Revenues
Total revenues	26,156.2	25,209.1	23,694.7
Retail automotive dealership | U.S.
Revenues
Total revenues	14,777.6	14,160.5	13,712.7
Retail automotive dealership | U.K.
Revenues
Total revenues	9,322.0	9,240.4	8,443.4
Retail automotive dealership | Germany, Italy, Japan, and Australia
Revenues
Total revenues	2,056.6	1,808.2	1,538.6
New vehicle | Retail automotive dealership
Revenues
Total revenues	12,055.9	11,273.3	10,050.5
Used vehicle | Retail automotive dealership
Revenues
Total revenues	8,770.7	8,919.5	9,011.6
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	811.1	838.6	848.1
Service and parts | Retail automotive dealership
Revenues
Total revenues	3,047.4	2,734.3	2,426.7
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 1,471.1	$ 1,443.4	$ 1,357.8