Quarterly report pursuant to Section 13 or 15(d)

Stockholders' Equity - Additional Information (Detail)

v2.4.1.9
Stockholders' Equity - Additional Information (Detail) (USD $)
In Thousands, except Share data, unless otherwise specified
 3 Months Ended 1 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Feb. 28, 2015
Dec. 31, 2014
Class Of Stock [Line Items]        
Partnership distributions, amount $ 1,241us-gaap_PartnersCapitalAccountDistributions $ 1,349us-gaap_PartnersCapitalAccountDistributions    
Distributions of partner incentive allocations of net income 18,568samg_DistributionsOfPartnerIncentiveAllocationsOfNetIncome 14,181samg_DistributionsOfPartnerIncentiveAllocationsOfNetIncome    
Accrued partner incentive allocations 5,291us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent     21,758us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent
Class B Common Stock        
Class Of Stock [Line Items]        
Class B common stock issued upon vesting of deferred equity units 126,616us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember 		  126,616us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember 		 
Exchange of Class B common stock for Class A common stock (18,000)samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember 		     
Class B Common Stock | Resale And Registration Rights Agreement        
Class Of Stock [Line Items]        
Exchange of Class B common stock for Class A common stock 18,000samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_ConversionOfStockByUniqueDescriptionAxis
= samg_ResaleAndRegistrationRightsAgreementMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember 		     
Slp        
Class Of Stock [Line Items]        
Accrued partner incentive allocations $ 4,241us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent
/ dei_LegalEntityAxis
= samg_SlpMember 		$ 4,114us-gaap_EmployeeRelatedLiabilitiesCurrentAndNoncurrent
/ dei_LegalEntityAxis
= samg_SlpMember