RECEIVABLES, NET AND CONTRACT ASSETS - Financial Assets (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Accounts, Notes, Loans and Financing Receivable
Contracts-in-transit	$ 196,500,000	$ 188,200,000
Vehicle receivables	103,500,000	90,900,000
Total contracts-in-transit and vehicle receivables	300,000,000.0	279,000,000.0
Less: allowance for doubtful accounts	300,000	600,000
Total contracts-in-transit and vehicle receivables, net	299,700,000	278,500,000
Accounts and notes receivable, net:
Accounts and notes receivables	228,600,000	204,700,000
Less: allowance for doubtful accounts	5,100,000	5,500,000
Total accounts and notes receivable, net	223,500,000	199,200,000
Total contract assets	55,200,000	47,900,000
Allowance for doubtful accounts	0	0
Manufacturer receivables
Accounts and notes receivable, net:
Accounts and notes receivables	119,400,000	94,600,000
Parts and service receivables
Accounts and notes receivable, net:
Accounts and notes receivables	69,700,000	68,000,000.0
F&I receivables
Accounts and notes receivable, net:
Accounts and notes receivables	28,700,000	30,000,000.0
Other
Accounts and notes receivable, net:
Accounts and notes receivables	$ 10,800,000	$ 12,100,000