ACQUISITIONS AND DIVESTITURES - Purchase Consideration (Details) - USD ($) $ in Millions			12 Months Ended
	Dec. 11, 2023	Dec. 17, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Business Acquisition [Line Items]
Cash, net of cash acquired			$ 1,500.0	$ 5.0	$ 3,660.4
Jim Koons Dealerships
Business Acquisition [Line Items]
Aggregate purchase price	$ 1,500.0
Jim Koons Dealerships | New Floor Plan Facility
Business Acquisition [Line Items]
Aggregate purchase price	256.1
Jim Koons Dealerships | Used Floor Plan Facility
Business Acquisition [Line Items]
Aggregate purchase price	$ 307.1
LHM Acquisition
Business Acquisition [Line Items]
Cash, net of cash acquired		$ 195.0
Aggregate purchase price		3,193.9
Common stock offering		666.9
Payable to sellers		6.0
LHM Acquisition | Senior Notes
Business Acquisition [Line Items]
Purchase price holdbacks		1,378.5
LHM Acquisition | Revolving Credit Facility
Business Acquisition [Line Items]
Purchase price holdbacks		200.0
LHM Acquisition | 2021 Real Estate Facility
Business Acquisition [Line Items]
Purchase price holdbacks		513.0
LHM Acquisition | New Vehicle Floor Plan Facility
Business Acquisition [Line Items]
Purchase price holdbacks		183.5
LHM Acquisition | Used Vehicle Floor Plan Facility
Business Acquisition [Line Items]
Purchase price holdbacks		$ 51.0