Annual report pursuant to Section 13 and 15(d)

Employee Benefit Plans - Status of Options Related to Stock Plans (Detail)

v2.4.1.9
Employee Benefit Plans - Status of Options Related to Stock Plans (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Options Outstanding Beginning Balance 1,518,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber    
Options Outstanding Exercised (179,000)us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised    
Options Outstanding Forfeited (275,000)us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod    
Options Outstanding Ending Balance 1,064,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 1,518,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber  
Options Outstanding Exercisable 1,064,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber    
Weighted Average Exercise Price Per Share, Beginning Balance $ 18.83us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Exercised $ 18.33us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Forfeited $ 23.87us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice    
Weighted Average Exercise Price Per Share, Ending Balance $ 17.62us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice $ 18.83us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice  
Weighted Average Exercise Price Per Share, Exercisable $ 17.62us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableWeightedAverageExercisePrice    
Weighted Average Remaining Contractual Term, Beginning Balance 2 years 2 months 12 days 2 years 6 months  
Weighted Average Remaining Contractual Term, Exercisable 2 years 2 months 12 days    
Aggregate Intrinsic Value, Beginning Balance $ 9,831us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue    
Aggregate Intrinsic Value, Ending Balance 10,444us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue 9,831us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue  
Aggregate Intrinsic Value, Exercisable 10,444us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1    
Intrinsic value of options exercised 1,187us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 1,657us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 7,427us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
Fair value of options vested     $ 426us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1
Minimum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Exercise Price Per Share, Beginning Balance $ 1.81sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansOutstandingExercisePriceRange
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Exercise Price Per Share, Exercised $ 1.81sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisedExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Exercise Price Per Share, Forfeited $ 18.73sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansForfeitedExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Exercise Price Per Share, Ending Balance $ 1.81sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansOutstandingExercisePriceRange
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Exercise Price Per Share, Exercisable $ 1.81sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisableExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
   
Maximum [Member]      
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]      
Exercise Price Per Share, Beginning Balance $ 30.07sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansOutstandingExercisePriceRange
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Exercise Price Per Share, Exercised $ 23.42sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisedExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Exercise Price Per Share, Forfeited $ 25.05sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansForfeitedExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Exercise Price Per Share, Ending Balance $ 25.05sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansOutstandingExercisePriceRange
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
   
Exercise Price Per Share, Exercisable $ 23.42sah_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisableExercisePriceRangeLowerRangeLimit
/ us-gaap_RangeAxis
= us-gaap_MaximumMember