Annual report pursuant to Section 13 and 15(d)

Notes Receivable from Partners - Schedule of Notes Receivable from Partners (Detail)

v2.4.1.9
Notes Receivable from Partners - Schedule of Notes Receivable from Partners (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Accounts Notes And Loans Receivable [Line Items]      
New notes receivable issued to partners $ 940samg_NotesReceivableFromNewPartnersIssuedAsCapitalContribution $ 455samg_NotesReceivableFromNewPartnersIssuedAsCapitalContribution $ 112samg_NotesReceivableFromNewPartnersIssuedAsCapitalContribution
Partners      
Accounts Notes And Loans Receivable [Line Items]      
Beginning balance 3,052us-gaap_NotesReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
3,410us-gaap_NotesReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
 
Repayment of notes (841)us-gaap_RepaymentOfNotesReceivableFromRelatedParties
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
(887)us-gaap_RepaymentOfNotesReceivableFromRelatedParties
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
 
Interest accrued and capitalized on notes receivable 61us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
74us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
 
New notes receivable issued to partners 940samg_NotesReceivableFromNewPartnersIssuedAsCapitalContribution
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
455samg_NotesReceivableFromNewPartnersIssuedAsCapitalContribution
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
 
Ending balance $ 3,212us-gaap_NotesReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember
$ 3,052us-gaap_NotesReceivableNet
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= samg_GeneralPartnerAndLimitedPartnerMember