INVENTORIES (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Components of Inventory [Line Items]
Total inventories	$ 413.8		$ 875.2
Lower of cost or market inventory reserves	4.5		6.7
New vehicles
Components of Inventory [Line Items]
Total inventories	121.9		640.0
Reduction of new vehicle inventory cost by automobile manufacturer incentives	(1.6)		(8.3)
Reduction to cost of sales	44.7	$ 31.5
Used vehicles
Components of Inventory [Line Items]
Total inventories	236.4		188.5
Parts and accessories
Components of Inventory [Line Items]
Total inventories	$ 55.5		$ 46.7