Annual report pursuant to Section 13 and 15(d)

Goodwill - Summary of Changes to Carrying Amount of Goodwill (Detail)

v2.4.1.9
Goodwill - Summary of Changes to Carrying Amount of Goodwill (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Goodwill [Line Items]    
Beginning, Gross balance $ 37,446us-gaap_GoodwillGross $ 33,306us-gaap_GoodwillGross
Beginning, Accumulated impairment losses (17,415)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss (17,415)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
Beginning, Net balance 20,031us-gaap_Goodwill 15,891us-gaap_Goodwill
Purchase price adjustments from earnouts (23)us-gaap_GoodwillPurchaseAccountingAdjustments 1,795us-gaap_GoodwillPurchaseAccountingAdjustments
Ending, Gross balance 37,423us-gaap_GoodwillGross 37,446us-gaap_GoodwillGross
Ending, Accumulated impairment losses (17,415)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss (17,415)us-gaap_GoodwillImpairedAccumulatedImpairmentLoss
Ending, Net balance 20,008us-gaap_Goodwill 20,031us-gaap_Goodwill
Ten-Sixty    
Goodwill [Line Items]    
Goodwill, Acquisition   2,345us-gaap_GoodwillAcquiredDuringPeriod
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember
Ending, Net balance   $ 2,345us-gaap_Goodwill
/ us-gaap_BusinessAcquisitionAxis
= samg_TenSixtyAssetManagementLlcMember