Obligations incurred related to finance leases associated with the acquisition of stores as of the acquisition date.

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Amount of vehicle floorplan payable, non-trade, assumed on the acquisition date.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Amount after tax of pro forma income from continuing operations as if the business combination had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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This element represents the amount of earnings or loss of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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This element represents the amount of revenue of the acquiree since the acquisition date included in the consolidated income statement for the reporting period.

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Amount of assets acquired at the acquisition date.

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Amount of other liabilities due within one year or within the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of assets, excluding financial assets and goodwill, that lack physical substance, having a projected indefinite period of benefit, acquired at the acquisition date.

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The amount of inventory recognized as of the acquisition date.

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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Amount recognized for assets, including goodwill, in excess of (less than) the aggregate liabilities assumed.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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The number of businesses acquired by the entity during the period.

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Acquisitions (Details) $ in Millions	12 Months Ended
Acquisitions (Details) $ in Millions	Dec. 31, 2021 USD ($) store	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($) store
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 1,235.3	$ 1,185.0	$ 1,501.9
Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Inventory	46.6
Property and equipment	282.8
Goodwill	51.6
Franchise rights - indefinite-lived	232.4
Other assets	17.7
Vehicle floorplan payable - non-trade	(15.1)
Other liabilities	(2.8)
Aggregate purchase price	613.2
Finance lease obligations	(180.5)
Cash used in business acquisition, net of cash acquired	432.7
Business Acquisition, Pro Forma Information [Abstract]
Amount of revenue included in our Consolidated Statement of Income	176.9
Amount of earnings included in our Consolidated Statement of Income	6.9
Pro-forma revenue	26,544.2	21,074.8
Pro-forma net income from continuing operations	1,407.0	404.1
Reporting Unit, Domestic [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	228.7	227.2	227.3
Reporting Unit, Domestic [Member] \| Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	1.5
Reporting Unit, Import [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	517.9	500.6	498.9
Reporting Unit, Import [Member] \| Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	15.3
Reporting Unit, Premium Luxury [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	484.1	457.2	714.9
Reporting Unit, Premium Luxury [Member] \| Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	30.3
Reporting Unit, Collision Centers [Member]
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	4.6	$ 0.0	$ 41.7
Reporting Unit, Collision Centers [Member] \| Series of Individually Immaterial Business Acquisitions
Business Combination, Recognized Identifiable Assets Acquired, Goodwill, and Liabilities Assumed, Net [Abstract]
Goodwill	$ 4.6
Dealerships [Member]
Acquisitions [Line Items]
Number of stores purchased \| store	20
Collision Center [Member]
Acquisitions [Line Items]
Number of stores purchased \| store	4
Parts Distribution Centers [Member]
Acquisitions [Line Items]
Number of stores purchased \| store			2