ACCOUNTS RECEIVABLE - Summary of Accounts Receivable (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	$ 1,003.8	$ 816.2
Less: Allowance for doubtful accounts	(4.5)	(3.1)
Total accounts receivable, net	999.3	813.1
Contracts in transit
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	458.8	432.5
Trade receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	156.3	122.6
Vehicle receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	170.3	105.4
Manufacturer receivables
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	207.8	151.9
Other receivables, current
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts receivable, before allowance for credit loss	$ 10.6	$ 3.8