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Business Combinations - Activity (Details) - item | 9 Months Ended
--- | ---
Sep. 30, 2017 | Sep. 30, 2016
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 | 8 | 13
Retail Commercial Truck Dealership |  |
Business combinations |  |
Number of retail locations acquired |  | 5

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- Definition Number of franchises acquired. + References No definition available. + Details
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Namespace Prefix: | pag_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Represents the number of retail locations acquired. + References No definition available. + Details
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Namespace Prefix: | pag_
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Balance Type: | na
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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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Namespace Prefix: | us-gaap_
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- Details
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Namespace Prefix: |
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- Details
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Period Type: |

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- Details
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Namespace Prefix: |
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- Details
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Namespace Prefix: |
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Period Type: |