Quarterly report pursuant to Section 13 or 15(d)

Commitments and Contingencies - Additional Information (Detail)

v2.4.1.9
Commitments and Contingencies - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Commitments And Contingencies [Line Items]      
Operating lease rent expense $ 917us-gaap_LeaseAndRentalExpense $ 902us-gaap_LeaseAndRentalExpense  
Sub-lease income 91us-gaap_OperatingLeasesRentExpenseSubleaseRentals1 102us-gaap_OperatingLeasesRentExpenseSubleaseRentals1  
Asset acquired under capital lease 11us-gaap_CapitalLeaseObligationsIncurred 289us-gaap_CapitalLeaseObligationsIncurred  
Depreciation expense 137us-gaap_Depreciation 121us-gaap_Depreciation  
Contingent consideration payments   1,679us-gaap_PaymentsToAcquireBusinessesGross  
MCG Acquisition | Contingent Consideration      
Commitments And Contingencies [Line Items]      
Contingent consideration percentage of EBITDA 22.00%samg_ContingentConsiderationPercentage
/ us-gaap_BusinessAcquisitionAxis
= samg_McgAcquisitionMember
/ us-gaap_ContingentConsiderationByTypeAxis
= samg_BusinessAcquisitionContingentConsiderationMember
   
Number of years contingent consideration adjusted annual EBITDA 5 years    
Contingent consideration payments 0us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= samg_McgAcquisitionMember
/ us-gaap_ContingentConsiderationByTypeAxis
= samg_BusinessAcquisitionContingentConsiderationMember
1,679us-gaap_PaymentsToAcquireBusinessesGross
/ us-gaap_BusinessAcquisitionAxis
= samg_McgAcquisitionMember
/ us-gaap_ContingentConsiderationByTypeAxis
= samg_BusinessAcquisitionContingentConsiderationMember
 
Capital Lease Assets      
Commitments And Contingencies [Line Items]      
Depreciation expense 17us-gaap_Depreciation
/ us-gaap_LeaseArrangementTypeAxis
= samg_CapitalLeaseAssetsMember
19us-gaap_Depreciation
/ us-gaap_LeaseArrangementTypeAxis
= samg_CapitalLeaseAssetsMember
 
Additional Office Space      
Commitments And Contingencies [Line Items]      
Operating lease rent expense, net 5us-gaap_OperatingLeasesRentExpenseNet
/ us-gaap_MajorPropertyClassAxis
= samg_AdditionalOfficeSpaceMember
   
Refundable security deposit 3us-gaap_SecurityDeposit
/ us-gaap_MajorPropertyClassAxis
= samg_AdditionalOfficeSpaceMember
   
Lease commencement date 2014-05-01    
Lease expires Jul. 31, 2019    
Number of rent free periods 3 months    
Office Equipment      
Commitments And Contingencies [Line Items]      
Lease expires Nov. 30, 2018    
Capital lease obligation 274us-gaap_CapitalLeaseObligations
/ us-gaap_MajorPropertyClassAxis
= us-gaap_OfficeEquipmentMember
  282us-gaap_CapitalLeaseObligations
/ us-gaap_MajorPropertyClassAxis
= us-gaap_OfficeEquipmentMember
Asset acquired under capital lease 321us-gaap_CapitalLeaseObligationsIncurred
/ us-gaap_MajorPropertyClassAxis
= us-gaap_OfficeEquipmentMember
   
Capital lease, period 5 years    
Capital lease, minimum monthly payment 5samg_CapitalLeasesMonthlyMinimumPayments
/ us-gaap_MajorPropertyClassAxis
= us-gaap_OfficeEquipmentMember
   
Letter of Credit      
Commitments And Contingencies [Line Items]      
Refundable security deposit 586us-gaap_SecurityDeposit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
  586us-gaap_SecurityDeposit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
Letter of Credit | Boston landlord      
Commitments And Contingencies [Line Items]      
Refundable security deposit 80us-gaap_SecurityDeposit
/ us-gaap_CreditFacilityAxis
= us-gaap_LetterOfCreditMember
/ dei_LegalEntityAxis
= samg_BostonLandlordMember
   
General, Administrative and Other Expenses      
Commitments And Contingencies [Line Items]      
Operating lease rent expense, net $ 826us-gaap_OperatingLeasesRentExpenseNet
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember
$ 800us-gaap_OperatingLeasesRentExpenseNet
/ us-gaap_IncomeStatementLocationAxis
= us-gaap_GeneralAndAdministrativeExpenseMember