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v3.20.4

Subsequent Events (Details) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) store | Dec. 31, 2018 USD ($) Business
Subsequent Event [Line Items] |  |  |
Number of franchises disposed |  | 1 | 2
Cash generated from disposition | $ 9.6 | $ 250.7 | $ 128.7

X
- Definition Number of franchises disposed. + References No definition available. + Details
Name: | sah_NumberOfFranchisesDisposed
Namespace Prefix: | sah_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Proceeds from dispositions of franchises. + References No definition available. + Details
Name: | sah_ProceedsFromDispositionsOfFranchises
Namespace Prefix: | sah_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
Name: | us-gaap_SubsequentEventLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration