Revenues - Retail Automotive Dealership (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Revenues
Total revenues	$ 6,975.4	$ 5,773.8
Retail automotive dealership
Revenues
Total revenues	6,029.2	5,206.9	$ 22,500.0
Retail automotive dealership | U.S.
Revenues
Total revenues	3,343.6	3,004.8
Retail automotive dealership | U.K.
Revenues
Total revenues	2,262.9	1,853.4
Retail automotive dealership | Germany, Italy, and Japan
Revenues
Total revenues	422.7	348.7
New vehicle | Retail automotive dealership
Revenues
Total revenues	2,445.5	2,421.4
Used vehicle | Retail automotive dealership
Revenues
Total revenues	2,422.9	1,808.0
Finance and insurance, net | Retail automotive dealership
Revenues
Total revenues	217.3	168.8
Service and parts | Retail automotive dealership
Revenues
Total revenues	586.2	503.2
Fleet and wholesale | Retail automotive dealership
Revenues
Total revenues	$ 357.3	$ 305.5