Quarterly report pursuant to Section 13 or 15(d)

Acquisitions - Additional Information (Detail)

v2.4.1.9
Acquisitions - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended 0 Months Ended 3 Months Ended 0 Months Ended 1 Months Ended
Mar. 31, 2014
Nov. 01, 2014
Mar. 31, 2015
Installment
Mar. 30, 2015
Mar. 28, 2013
Dec. 31, 2013
Apr. 30, 2013
Dec. 31, 2014
Business Acquisition [Line Items]                
Cash consideration under Asset Purchase Agreement $ 1,679us-gaap_PaymentsToAcquireBusinessesGross              
Promissory Note                
Business Acquisition [Line Items]                
Number of installments     4samg_DebtInstrumentNumberOfInstallment
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
         
Installment amount payable   900us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
           
Jamison                
Business Acquisition [Line Items]                
Cash consideration under Asset Purchase Agreement       3,550us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Equity consideration for SLP acquired       3,967us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn out payments percentage on EBITDA remainder of fiscal year       20.00%samg_EarnOutPaymentsPercentageOnEBITDARemainderOfFiscalYear
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn out payments percentage on EBITDA due in two years       20.00%samg_EarnOutPaymentsPercentageOnEBITDADueInTwoYears
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn out payments percentage on EBITDA due in three years       20.00%samg_EarnOutPaymentsPercentageOnEBITDADueInThreeYears
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn out payments percentage on EBITDA due in four years       20.00%samg_EarnOutPaymentsPercentageOnEBITDADueInFourYears
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn out payments percentage on EBITDA due in five years       20.00%samg_EarnOutPaymentsPercentageOnEBITDADueInFiveYears
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Earn Out Payments Percentage On EBITDA Due thereafter       20.00%samg_EarnOutPaymentsPercentageOnEBITDADueThereafter
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
       
Jamison | Seller Note                
Business Acquisition [Line Items]                
Promissory note issued       612samg_BusinessAcquisitionCostOfAcquiredEntityPromissoryNotesIssued
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
/ us-gaap_DebtInstrumentAxis
= samg_SellerNoteMember
       
Interest on principal amount       5.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
/ us-gaap_DebtInstrumentAxis
= samg_SellerNoteMember
       
Jamison | Principals Notes                
Business Acquisition [Line Items]                
Promissory note issued       1,771samg_BusinessAcquisitionCostOfAcquiredEntityPromissoryNotesIssued
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
/ us-gaap_DebtInstrumentAxis
= samg_PrincipalsNotesMember
       
Interest on principal amount       5.00%us-gaap_DebtInstrumentInterestRateEffectivePercentage
/ us-gaap_BusinessAcquisitionAxis
= samg_JamisonMember
/ us-gaap_DebtInstrumentAxis
= samg_PrincipalsNotesMember
       
Milbank                
Business Acquisition [Line Items]                
Equity consideration for SLP acquired     1,325us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= samg_MilbankMember
        1,325us-gaap_BusinessCombinationContingentConsiderationLiability
/ us-gaap_BusinessAcquisitionAxis
= samg_MilbankMember
Outstanding note payable     564us-gaap_NotesPayableCurrent
/ us-gaap_BusinessAcquisitionAxis
= samg_MilbankMember
         
Ten-Sixty                
Business Acquisition [Line Items]                
Cash consideration under Asset Purchase Agreement         2,500us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
     
Promissory note issued         1,479samg_BusinessAcquisitionCostOfAcquiredEntityPromissoryNotesIssued
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
     
Acquisition of assets         1,900,000us-gaap_AssetsUnderManagementCarryingAmount
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
     
Ten-Sixty | Promissory Note                
Business Acquisition [Line Items]                
Number of installments     2samg_DebtInstrumentNumberOfInstallment
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
         
Installment amount payable           218us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
218us-gaap_DebtInstrumentPeriodicPaymentPrincipal
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
 
Quarterly installments from June 30, 2014 through March 31, 2017     87samg_DebtInstrumentQuarterlyPaymentPrincipal
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember
         
Principal on fixed rate notes, interest rate     5.00%us-gaap_LongTermDebtPercentageBearingFixedInterestRate
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_LongtermDebtTypeAxis
= samg_PromissoryNotesPayableMember