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Business Combinations - Activity (Details) - item | 9 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017
The Car People |  |
Business combinations |  |
Number of retail locations acquired | 4 |
CarSense |  |
Business combinations |  |
Number of retail locations acquired |  | 5
CarShop |  |
Business combinations |  |
Number of retail locations acquired |  | 5
Retail Automotive Dealership |  |
Business combinations |  |
Number of acquired franchises | 4 | 8
Retail Commercial Truck Dealership |  |
Business combinations |  |
Number of retail locations acquired | 1 |

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- Definition Number of franchises acquired. + References No definition available. + Details
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- Definition Represents the number of retail locations acquired. + References No definition available. + Details
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- Definition 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. + References No definition available. + Details
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- Details
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- Details
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- Details
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- Details
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