Quarterly report pursuant to Section 13 or 15(d)

Property and Equipment - Additional Information (Detail)

v2.4.1.9
Property and Equipment - Additional Information (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Property Plant And Equipment [Line Items]    
Capital expenditure $ 46,800,000us-gaap_PropertyPlantAndEquipmentAdditions $ 21,500,000us-gaap_PropertyPlantAndEquipmentAdditions
Asset impairment charges 6,192,000sah_AssetImpairmentChargesContinuingOperations 3,000sah_AssetImpairmentChargesContinuingOperations
Franchised Dealerships [Member]    
Property Plant And Equipment [Line Items]    
Asset impairment charges 4,800,000sah_AssetImpairmentChargesContinuingOperations
/ us-gaap_StatementBusinessSegmentsAxis
= sah_FranchisedDealershipsMember
 
Echo Park [Member]    
Property Plant And Equipment [Line Items]    
Asset impairment charges $ 1,400,000sah_AssetImpairmentChargesContinuingOperations
/ us-gaap_StatementBusinessSegmentsAxis
= sah_EchoParkMember