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INVENTORIES (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Components of Inventory [Line Items]
Total inventories	$ 2,318.9		$ 2,318.9		$ 1,978.8
Reduction of new vehicle inventory cost by automobile manufacturer incentives	(9.8)		(9.8)		(9.7)
Held-for-sale
Components of Inventory [Line Items]
Total inventories	20.0		20.0		58.7
New vehicles
Components of Inventory [Line Items]
Total inventories	1,688.5		1,688.5		1,450.6
Reduction of new vehicle inventory cost by automobile manufacturer incentives	(16.3)		(16.3)		(13.8)
Reduction to cost of sales	32.4	$ 27.5	93.9	$ 80.7
Used vehicles
Components of Inventory [Line Items]
Total inventories	469.6		469.6		382.1
Parts and accessories
Components of Inventory [Line Items]
Total inventories	$ 160.8		$ 160.8		$ 146.0

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Components of Inventory [Line Items]

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Amount of inventory reserves for last-in first-out (LIFO) and other inventory valuation methods.

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Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

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