Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
Segment Information (Details) $ in Millions	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) item	Jun. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)
Segment Reporting Information
Number of reportable segments \| item			4
Number of operating segments \| item			6
Revenues and segment income by reportable segment
Revenues	$ 5,755.8	$ 5,940.3	$ 11,320.2	$ 11,687.2
Segment income	159.9	176.2	$ 293.7	320.5
Operating segments
Segment Reporting Information
Number of reportable segments \| item			1
Retail Automotive Dealership
Revenues and segment income by reportable segment
Revenues	5,196.3	5,455.5	$ 10,287.5	10,751.5	$ 20,800.0
Retail Automotive Dealership \| Operating segments
Revenues and segment income by reportable segment
Revenues	5,196.3	5,455.5	10,287.5	10,751.5
Segment income	98.1	117.0	183.0	223.6
Retail Commercial Truck Dealership
Revenues and segment income by reportable segment
Revenues	426.8	338.8	759.1	631.2
Retail Commercial Truck Dealership \| Operating segments
Revenues and segment income by reportable segment
Revenues	426.8	338.8	759.1	631.2
Segment income	18.9	16.0	34.8	28.1
Other \| Operating segments
Revenues and segment income by reportable segment
Revenues	132.7	146.0	273.6	304.5
Segment income	4.9	8.2	12.1	17.8
Non-Automotive Investments \| Operating segments
Revenues and segment income by reportable segment
Segment income	$ 38.0	$ 35.0	$ 63.8	$ 51.0