Inventory and Vehicle Floorplan Payable (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Floorplan Payable [Line Items]
Vehicle floorplan facilities, amount outstanding	$ 2,109.3	$ 1,457.6
Used vehicle floorplan facilities, remaining borrowing capacity	107.8
Used vehicle floorplan facilities, current borrowing capacity	$ 0.3
New Vehicle Floorplan Facilities [Member]
Floorplan Payable [Line Items]
Vehicle floorplan facilities, weighted average interest rates on amounts outstanding	5.90%	1.60%
Vehicle floorplan facilities, maximum borrowing capacity	$ 4,700.0
Vehicle floorplan facilities, amount outstanding	$ 1,500.0
Used Vehicle Floorplan Facilities [Member]
Floorplan Payable [Line Items]
Vehicle floorplan facilities, weighted average interest rates on amounts outstanding	5.90%	1.80%
Vehicle floorplan facilities, maximum borrowing capacity	$ 683.6
Vehicle floorplan facilities, amount outstanding	$ 575.8