Annual report pursuant to Section 13 and 15(d)

Acquisitions - Summary of Final Amounts Allocated to Acquired Assets and Assumed Liabilities (Detail)

v2.4.1.9
Acquisitions - Summary of Final Amounts Allocated to Acquired Assets and Assumed Liabilities (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Business Acquisition [Line Items]      
Goodwill $ 20,008us-gaap_Goodwill $ 20,031us-gaap_Goodwill $ 15,891us-gaap_Goodwill
MW Commodity Advisors, LLC      
Business Acquisition [Line Items]      
Receivables   7us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets
/ us-gaap_BusinessAcquisitionAxis
= samg_MwCommodityAdvisorsLlcMember
 
Liabilities   (7)us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities
/ us-gaap_BusinessAcquisitionAxis
= samg_MwCommodityAdvisorsLlcMember
 
Total fair value of net tangible assets acquired   0us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= samg_MwCommodityAdvisorsLlcMember
 
Goodwill   147us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= samg_MwCommodityAdvisorsLlcMember
 
Total purchase consideration   147us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= samg_MwCommodityAdvisorsLlcMember
 
Ten-Sixty      
Business Acquisition [Line Items]      
Total fair value of net tangible assets acquired   0us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
 
Goodwill   2,345us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
 
Total purchase consideration   4,092us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
 
Ten-Sixty | Customer Relationships      
Business Acquisition [Line Items]      
Intangible asset   1,650us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_CustomerRelationshipsMember
 
Ten-Sixty | Non-compete Agreements      
Business Acquisition [Line Items]      
Intangible asset   $ 97us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
/ us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_NoncompeteAgreementsMember