Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues
Total revenues	$ 29,527.4	$ 27,814.8	$ 25,554.7
U.S.
Revenues
Total revenues	17,186.5	16,801.7	15,275.9
Retail automotive dealership
Revenues
Total revenues	25,209.1	23,694.7	22,513.3
Retail automotive dealership | U.S.
Revenues
Total revenues	14,160.5	13,712.7	13,075.8
Retail automotive dealership | U.K.
Revenues
Total revenues	9,240.4	8,443.4	7,984.1
Retail automotive dealership | Germany, Italy, and Japan
Revenues
Total revenues	1,808.2	1,538.6	1,453.4
New vehicle | Retail automotive dealership
Revenues
Total revenues	11,273.3	10,050.5	9,843.2
Used vehicle | Retail automotive dealership
Revenues
Total revenues	8,919.5	9,011.6	8,549.0
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	838.6	848.1	780.5
Service and parts | Retail automotive dealership
Revenues
Total revenues	2,734.3	2,426.7	2,165.6
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 1,443.4	$ 1,357.8	$ 1,175.0