Annual report pursuant to Section 13 and 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
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
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.      
Compensation expense $ 1,043us-gaap_AllocatedShareBasedCompensationExpense $ 2,222us-gaap_AllocatedShareBasedCompensationExpense $ 1,388us-gaap_AllocatedShareBasedCompensationExpense  
Cash distributions on awards 1samg_CashDistributionPaidOnAwards 13samg_CashDistributionPaidOnAwards 17samg_CashDistributionPaidOnAwards  
Unrecognized compensation expense related to unvested awards 168us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions 906us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions    
Recognition period of unrecognized compensation expense related to unvested awards 7 months 24 days 1 year 1 month 28 days    
Distribution of partnership units for each limited partnership unit prior to the consummation of the IPO 19.64samg_DistributionOfPartnershipUnitsForEachLimitedPartnershipUnitPriorToConsummationOfInitialPublicOffering      
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]        
Compensation expense 109us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
245us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
147us-gaap_AllocatedShareBasedCompensationExpense
/ 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 $ 30us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
$ 260us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember
$ 63us-gaap_EmployeeServiceShareBasedCompensationCashFlowEffectCashUsedToSettleAwards
/ us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis
= us-gaap_DeferredCompensationShareBasedPaymentsMember