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Summary of Significant Accounting Policies - Summary of Operating Lease Exit Accruals (Detail) (USD $) In Thousands, unless otherwise specified | 9 Months Ended
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Sep. 30, 2014
Accounting Policies [Abstract] |
Balance, December 31, 2013 | $ 27,234
Lease exit expense | (272)
Payments | (5,445)
Lease buyout | (1,556)
Balance, September 30, 2014 | $ 19,961

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

X
- 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

X
- 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

X
- 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

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