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v2.4.1.9

Property and Equipment - Additional Information (Detail) (USD $) | 3 Months Ended
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Mar. 31, 2015 | Mar. 31, 2014
Property Plant And Equipment [Line Items] |  |
Capital expenditure | $ 46,800,000 us-gaap_PropertyPlantAndEquipmentAdditions | $ 21,500,000 us-gaap_PropertyPlantAndEquipmentAdditions
Asset impairment charges | 6,192,000 sah_AssetImpairmentChargesContinuingOperations | 3,000 sah_AssetImpairmentChargesContinuingOperations
Franchised Dealerships [Member] |  |
Property Plant And Equipment [Line Items] |  |
Asset impairment charges | 4,800,000 sah_AssetImpairmentChargesContinuingOperations / us-gaap_StatementBusinessSegmentsAxis = sah_FranchisedDealershipsMember |
Echo Park [Member] |  |
Property Plant And Equipment [Line Items] |  |
Asset impairment charges | $ 1,400,000 sah_AssetImpairmentChargesContinuingOperations / us-gaap_StatementBusinessSegmentsAxis = sah_EchoParkMember |

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- Definition Asset impairment charges continuing operations. + References No definition available. + Details
Name: | sah_AssetImpairmentChargesContinuingOperations
Namespace Prefix: | sah_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Amount of acquisition of long-lived, physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, furniture and fixtures, and computer equipment. + References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAdditions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_PropertyPlantAndEquipmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=sah_EchoParkMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementBusinessSegmentsAxis=sah_FranchisedDealershipsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |