ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Increase (Decrease) in AOCI
Beginning balance	$ 2,674.4	$ 2,237.5
Other comprehensive income (loss) before reclassifications:
Pre-tax	14.3	0.9
Tax effect	(4.5)	2.1
Amount reclassified from accumulated other comprehensive income (loss):
Provision (benefit) for income taxes	2.4	2.7
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	2.1	(5.7)
Ending balance	2,772.4	2,352.5
Interest Rate Swaps
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	(0.2)	(4.0)
Floorplan interest expense (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	(5.3)	(3.3)
Other interest expense, net (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	(4.6)	(4.2)
Accumulated Other Comprehensive Income (loss)
Increase (Decrease) in AOCI
Beginning balance	28.1	22.5
Amount reclassified from accumulated other comprehensive income (loss):
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	2.1	(5.7)
Ending balance	30.3	16.7
Accumulated Income (Loss) On Foreign Currency Translation
Increase (Decrease) in AOCI
Beginning balance	(37.4)	(61.1)
Other comprehensive income (loss) before reclassifications:
Pre-tax	(4.5)	9.8
Tax effect	0.0	0.0
Amount reclassified from accumulated other comprehensive income (loss):
Provision (benefit) for income taxes	0.0	0.0
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	(4.5)	9.8
Ending balance	(41.9)	(51.3)
Accumulated Income (Loss) On Foreign Currency Translation | Interest Rate Swaps
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	0.0	0.0
Accumulated Income (Loss) On Foreign Currency Translation | Floorplan interest expense (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	0.0	0.0
Accumulated Income (Loss) On Foreign Currency Translation | Other interest expense, net (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	0.0	0.0
Accumulated Income (Loss) On Interest Rate Swaps
Increase (Decrease) in AOCI
Beginning balance	65.6	83.6
Other comprehensive income (loss) before reclassifications:
Pre-tax	18.8	(8.8)
Tax effect	(4.5)	2.1
Amount reclassified from accumulated other comprehensive income (loss):
Provision (benefit) for income taxes	2.4	2.7
OTHER COMPREHENSIVE INCOME (LOSS), NET OF TAX	6.6	(15.5)
Ending balance	72.2	68.1
Accumulated Income (Loss) On Interest Rate Swaps | Interest Rate Swaps
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	(0.2)	(4.0)
Accumulated Income (Loss) On Interest Rate Swaps | Floorplan interest expense (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	(5.3)	(3.3)
Accumulated Income (Loss) On Interest Rate Swaps | Other interest expense, net (pre-tax)
Amount reclassified from accumulated other comprehensive income (loss):
Pre-tax	$ (4.6)	$ (4.2)