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Summary of Significant Accounting Policies - Summary of Operating Lease Exit Accruals (Detail) (USD $) In Thousands, unless otherwise specified | 3 Months Ended
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Mar. 31, 2015
Accounting Policies [Abstract] |
Balance, December 31, 2014 | $ 18,962 sah_LeaseExitAccruals
Lease exit expense | 503 sah_LeaseExitExpense
Payments | (1,562)sah_LeaseExitPayment
Balance, March 31, 2015 | $ 17,903 sah_LeaseExitAccruals

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- Definition Lease exit accruals. + References No definition available. + Details
Name: | sah_LeaseExitAccruals
Namespace Prefix: | sah_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Lease exit expense. + References No definition available. + Details
Name: | sah_LeaseExitExpense
Namespace Prefix: | sah_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Lease exit payment. + References No definition available. + Details
Name: | sah_LeaseExitPayment
Namespace Prefix: | sah_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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