Inventory And Vehicle Floorplan Payable (Components Of Inventory) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Inventory [Line Items]
Inventory	$ 1,496.6	$ 2,598.5
New Vehicle [Member]
Inventory [Line Items]
Inventory	387.5	1,761.9
Used Vehicle [Member]
Inventory [Line Items]
Inventory	898.1	648.4
Parts and Service [Member]
Inventory [Line Items]
Inventory	$ 211.0	$ 188.2

Amount after valuation and LIFO reserves of inventory expected to be sold, or consumed within one year or operating cycle, if longer.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Publisher FASB
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