Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measurements - Fair Value and Carrying Value of Fixed Rate Long-Term Debt (Detail)

v2.4.1.9
Fair Value Measurements - Fair Value and Carrying Value of Fixed Rate Long-Term Debt (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
7.0% Senior Subordinated Notes Due 2022 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value $ 218,000us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
$ 216,000us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
Long-term Debt, Carrying Value 198,593us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
198,556us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_SevenPercentSeniorSubordinateNoteDueTwoThousandTwentyTwoMember
5.0% Senior Subordinated Notes due 2023 [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 299,250us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
294,000us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
Long-term Debt, Carrying Value 300,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
300,000us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_FivePercentSeniorSubordinateNoteDueTwoThousandTwentyThreeMember
Mortgage Loan at Fix Interest Rate [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 152,137us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageLoanAtFixInterestRateMember
152,240us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageLoanAtFixInterestRateMember
Long-term Debt, Carrying Value 145,732us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageLoanAtFixInterestRateMember
147,554us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_MortgageLoanAtFixInterestRateMember
Assumed Notes [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 3,494us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember
4,365us-gaap_LongTermDebtFairValue
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember
Long-term Debt, Carrying Value 3,563us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember
4,474us-gaap_LongTermDebt
/ us-gaap_LongtermDebtTypeAxis
= sah_AssumedNotesMember
Other [Member]    
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]    
Long-term Debt, Fair Value 4,530us-gaap_LongTermDebtFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_OtherDebtSecuritiesMember
4,588us-gaap_LongTermDebtFairValue
/ us-gaap_DebtSecurityAxis
= us-gaap_OtherDebtSecuritiesMember
Long-term Debt, Carrying Value $ 4,816us-gaap_LongTermDebt
/ us-gaap_DebtSecurityAxis
= us-gaap_OtherDebtSecuritiesMember
$ 4,884us-gaap_LongTermDebt
/ us-gaap_DebtSecurityAxis
= us-gaap_OtherDebtSecuritiesMember