Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Additional Information (Detail)

v2.4.1.9
Equity-Based Compensation - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Nov. 02, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Equity program, description The Deferred Equity Unit represents the unsecured right to receive one unit of SLP or the equivalent cash value of up to 50% (or such other percentage as may be determined by the Company’s Executive Committee) of SLP’s units issuable upon the vesting of any such Deferred Equity Units and the remaining 50% in units upon the vesting of any such Deferred Equity Units.      
Performance Unit, description The Performance Unit represents the unsecured right to receive one unit of SLP for every two units of SLP issuable upon the vesting of any such Deferred Equity Units.      
Equity-based compensation $ 115us-gaap_ShareBasedCompensation $ 514us-gaap_ShareBasedCompensation    
Cash distributions on awards 0samg_CashDistributionPaidOnAwards 1samg_CashDistributionPaidOnAwards    
Unrecognized compensation expense related to unvested awards 63us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions   168us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions  
Recognition period of unrecognized compensation expense related to unvested awards 10 months 21 days   7 months 24 days  
Estimated percentage of awards to be forfeited 10.00%samg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeiturePercentage      
Estimated service period 4 years      
2012 Equity Incentive Plan        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Shares reserved for issuance 1,670,960us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_PlanNameAxis
= samg_TwoThousandTwelveEquityIncentivePlanMember
     
Shares reserved for issuance, authorized       1,687,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= samg_TwoThousandTwelveEquityIncentivePlanMember
Performance Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Equity-based compensation 16us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
42us-gaap_ShareBasedCompensation
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
   
Deferred Equity Units        
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]        
Vested awards settled in cash $ 0us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
$ 30us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember