Inventory and Vehicle Floorplan Payable (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Floorplan Payable [Line Items]
Service loaner and rental vehicle inventory	$ 465.4	$ 455.4
Vehicle floorplan facilities, amount outstanding	$ 3,759.0	$ 3,828.3
New Vehicle Floorplan Facilities
Floorplan Payable [Line Items]
Vehicle floorplan facilities, weighted-average interest rate (percent)	5.10%	5.40%
Vehicle floorplan facilities, maximum borrowing capacity	$ 4,700.0
Vehicle floorplan facilities, amount outstanding	$ 3,200.0
Used Vehicle Floorplan Facilities
Floorplan Payable [Line Items]
Vehicle floorplan facilities, weighted-average interest rate (percent)	5.10%	5.20%
Vehicle floorplan facilities, maximum borrowing capacity	$ 788.5
Vehicle floorplan facilities, amount outstanding	595.7
Used vehicle floorplan facilities, unused borrowing capacity	192.8
Used vehicle floorplan facilities, remaining borrowing capacity	$ 0.3