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INVENTORIES (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2024
Components of Inventory [Line Items]
Total inventories	$ 1,942.2		$ 1,942.2		$ 1,978.8
Reduction of new vehicle inventory cost by automobile manufacturer incentives	(9.3)		(9.3)		(9.7)
Held-for-sale
Components of Inventory [Line Items]
Total inventories	49.4		49.4		58.7
New vehicles
Components of Inventory [Line Items]
Total inventories	1,377.4		1,377.4		1,450.6
Reduction of new vehicle inventory cost by automobile manufacturer incentives	(13.7)		(13.7)		(13.8)
Reduction to cost of sales	32.3	$ 27.0	61.4	$ 53.3
Used vehicles
Components of Inventory [Line Items]
Total inventories	420.0		420.0		382.1
Parts and accessories
Components of Inventory [Line Items]
Total inventories	$ 144.7		$ 144.7		$ 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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