INVENTORIES (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Components of Inventory [Line Items]
Inventories, net	$ 894.9	$ 917.2
Lower of cost or market inventory reserves	6.5	6.2
New Vehicles [Member]
Components of Inventory [Line Items]
Inventories, net	720.6	739.2
Reduction of new vehicle inventory cost by automobile manufacturer incentives	8.2	9.6
Reduction to new vehicle cost of sales by automobile manufacturer incentives	40.6	38.8	$ 30.3
Used Vehicles [Member]
Components of Inventory [Line Items]
Inventories, net	132.7	134.1
Parts and Accessories [Member]
Components of Inventory [Line Items]
Inventories, net	$ 41.6	$ 43.9