ACQUISITIONS AND DIVESTITURES - Other Acquisitions (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) dealership_location franchise	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Business Acquisition [Line Items]
Goodwill	$ 2,009.0	$ 1,783.4	$ 2,271.7
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Inventories, net	37.5
Real estate	99.9
Property and equipment, net	4.2
Goodwill	110.5
Intangible franchise rights	228.2
Loaner vehicles	8.9
Other	(3.5)
Net assets acquired	$ 485.7
Colorado | Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Number of franchises acquired (in franchises) | franchise	11
Number of dealership locations acquired (in dealership locations) | dealership_location	10
Indiana | Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Number of franchises acquired (in franchises) | franchise	3
Number of dealership locations acquired (in dealership locations) | dealership_location	1