Business Acquisitions and Dispositions - Additional Information (Details)  | 
9 Months Ended | |
|---|---|---|
| 
 Sep. 30, 2020  
USD ($)  
Business 
 | 
 Sep. 30, 2019  
USD ($)  
Business 
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| Business Combinations [Abstract] | ||
| Number of acquired franchises | 0 | |
| Business Acquisition [Line Items] | ||
| Number of franchises disposed | 4 | |
| Net cash generated from disposition | $ | $ 8,800,000 | |
| Number of franchises terminated | 1 | |
| Proceeds from sales of dealerships | $ | $ 8,806,000 | $ 130,086,000 | 
| Luxury franchise | ||
| Business Acquisition [Line Items] | ||
| Number of franchises terminated | 1 | 1 | 
| Mid-line import franchise | ||
| Business Acquisition [Line Items] | ||
| Net cash generated from disposition | $ | $ 130,100 | |
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- References No definition available. 
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- References No definition available. 
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- Definition Proceeds From Dispositions Of Franchises No definition available. 
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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. No definition available. 
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- References No definition available. 
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- Definition The number of businesses acquired by the entity during the period. No definition available. 
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- Definition This element represents the cash inflow during the period from the sale of a component of the entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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- Details 
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- Details 
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