Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt - Additional Information (Detail)

v2.4.1.9
Long-Term Debt - Additional Information (Detail) (USD $)
 3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Jul. 02, 2012
May 09, 2013
Dec. 31, 2014
Debt Instrument [Line Items]          
Total debt $ 794,625,000us-gaap_DebtInstrumentCarryingAmount       $ 773,412,000us-gaap_DebtInstrumentCarryingAmount
Incremental interest expense 2,300,000sah_InterestExpenseNetCashFlowSwaps 2,900,000sah_InterestExpenseNetCashFlowSwaps      
Net expense expected to be reclassified 4,300,000us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet        
Derivative Instruments and Hedging Activities [Member]          
Debt Instrument [Line Items]          
Fair value of swap positions 12,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember 		      11,100,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Benefits and charges related to cash flow swaps not designated as hedges 100,000sah_CashFlowSwapsNotDesignatedAsHedgeBenefitsAndCharges
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember 		       
Derivative Instruments and Hedging Activities [Member] | Other Accrued Liabilities [Member]          
Debt Instrument [Line Items]          
Fair value of swap positions 7,000,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= sah_OtherAccruedLiabilitiesMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember 		      8,200,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= sah_OtherAccruedLiabilitiesMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Derivative Instruments and Hedging Activities [Member] | Other Long-Term Liabilities [Member]          
Debt Instrument [Line Items]          
Fair value of swap positions 5,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= sah_OtherLongTermLiabilitiesMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember 		      3,500,000us-gaap_DerivativeFairValueOfDerivativeLiability
/ us-gaap_BalanceSheetLocationAxis
= sah_OtherLongTermLiabilitiesMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
Derivative Instruments and Hedging Activities [Member] | Other Assets [Member]          
Debt Instrument [Line Items]          
Fair value of swap positions         600,000us-gaap_DerivativeFairValueOfDerivativeAsset
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherAssetsMember
/ us-gaap_HedgingDesignationAxis
= us-gaap_DesignatedAsHedgingInstrumentMember
2014 Revolving Credit Facility [Member]          
Debt Instrument [Line Items]          
Current borrowing capacity 225,000,000us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
Maximum borrowing capacity 275,000,000us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
Borrowing base 181,800,000sah_RevolvingBorrowingBase
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
Letters of credit outstanding amount 25,500,000us-gaap_LettersOfCreditOutstandingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
Total debt 0us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
Borrowing availability amount 156,300,000us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
/ us-gaap_LongtermDebtTypeAxis
= sah_TwoThousandFourteenRevolvingCreditFacilityMember 		       
7.0% Senior Subordinated Notes Due 2022 [Member]          
Debt Instrument [Line Items]          
Total debt 200,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember 		      200,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
Principal amount     200,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember 		   
Stated interest rate on debt agreement 7.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember 		  7.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember 		  7.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
Notes maturity date Jul. 15, 2022        
Interest payable description semi-annually in arrears on January 15 and July 15 of each year        
Subordinated Notes [Member]          
Debt Instrument [Line Items]          
Notes issued at a price of principal amount     99.11%sah_NotesIssuedAtPriceOfPrincipalAmount
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorSubordinatedNotesMember 		   
Notes issued yield maturity, percentage     7.125%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_LongtermDebtTypeAxis
= us-gaap_SeniorSubordinatedNotesMember 		   
5.0% Senior Subordinated Notes due 2023 [Member]          
Debt Instrument [Line Items]          
Total debt 300,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember 		      300,000,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
Principal amount       300,000,000us-gaap_DebtInstrumentFaceAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember 		 
Stated interest rate on debt agreement 5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember 		    5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember 		5.00%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
Notes issued at a price of principal amount       100.00%sah_NotesIssuedAtPriceOfPrincipalAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember 		 
Notes maturity date May 15, 2023        
Interest payable description semi-annually in arrears on May 15 and November 15 of each year        
Assumed Notes [Member]          
Debt Instrument [Line Items]          
Total debt 3,500,000us-gaap_DebtInstrumentCarryingAmount
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember 		       
Stated interest rate on debt agreement 5.35%us-gaap_DebtInstrumentInterestRateStatedPercentage
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember 		       
Premium recorded on notes payable 7,300,000sah_DebtInstrumentsFairValueDisclosurePremiumRecorded
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember 		       
Premium associated with notes 100,000us-gaap_DebtInstrumentUnamortizedPremium
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember 		       
Notes payable due date October 2015 and August 2016        
Mortgage Notes [Member]          
Debt Instrument [Line Items]          
Notes payable due date Between 2015 and 2033        
Debt weighted average interest rate on note 3.57%us-gaap_DebtWeightedAverageInterestRate
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageNotesMember 		       
Mortgage financing aggregate $ 288,000,000us-gaap_SecuredDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageNotesMember 		       
Percentage of operating properties related to mortgage financing 30.00%sah_PercentageOfMortgageOperatingProperties
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageNotesMember 		       
2014 Credit Facility [Member]          
Debt Instrument [Line Items]          
Maturity date of revolving credit facility and floor plan facility Aug. 15, 2019        
Minimum EBTDAR to rent ratio 359.00%sah_MinimumEbtdarToRentRatio
/ us-gaap_CreditFacilityAxis
= sah_TwoThousandFourteenCreditFacilityMember 		       
2014 Credit Facility [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
EBTDAR to rent ratio 100.00%sah_EbtdarToRentRatio
/ us-gaap_CreditFacilityAxis
= sah_TwoThousandFourteenCreditFacilityMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember 		       
2014 Credit Facility [Member] | Required Ratio [Member]          
Debt Instrument [Line Items]          
Minimum EBTDAR to rent ratio 150.00%sah_MinimumEbtdarToRentRatio
/ us-gaap_CreditFacilityAxis
= sah_TwoThousandFourteenCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= sah_RequiredRatioMember 		       
2014 Credit Facility [Member] | Required Ratio [Member] | Minimum [Member]          
Debt Instrument [Line Items]          
EBTDAR to rent ratio 100.00%sah_EbtdarToRentRatio
/ us-gaap_CreditFacilityAxis
= sah_TwoThousandFourteenCreditFacilityMember
/ us-gaap_LongtermDebtTypeAxis
= sah_RequiredRatioMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember