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Business and Summary of Significant Accounting Policies - Business and Credit Risk Concentrations (Details) - Due from Manufacturers | 12 Months Ended
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Dec. 31, 2020
Toyota/Lexus |
Concentration Risk [Line Items] |
Percentage of Company's new vehicle sales volume more than which no other manufacturer accounted for | 23.90%
Volkswagen/Audi/Porsche/SEAT/SKODA |
Concentration Risk [Line Items] |
Percentage of Company's new vehicle sales volume more than which no other manufacturer accounted for | 14.90%
BMW/MINI |
Concentration Risk [Line Items] |
Percentage of Company's new vehicle sales volume more than which no other manufacturer accounted for | 11.40%
Ford/Lincoln |
Concentration Risk [Line Items] |
Percentage of Company's new vehicle sales volume more than which no other manufacturer accounted for | 10.50%

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