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Stockholders' Equity - Class B Common Stock (Detail) (Class B Common Stock)
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1 Months Ended |
12 Months Ended |
3 Months Ended |
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May 31, 2014
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Feb. 28, 2014
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2014
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Sep. 30, 2014
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| Class Of Stock [Line Items] |
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| Stock repurchased/surrendered and cancelled , transaction date |
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Feb. 01, 2014
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| Common stock issued upon vesting of deferred equity units, transaction date |
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Feb. 01, 2014
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| Balance, Shares |
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4,464,617us-gaap_CommonStockSharesOutstanding
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| Common stock repurchased/surrendered and cancelled |
(5,893)us-gaap_StockRepurchasedDuringPeriodShares
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(16,530)us-gaap_StockRepurchasedDuringPeriodShares
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(16,530)us-gaap_StockRepurchasedDuringPeriodShares
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| Common stock issued |
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261,958us-gaap_StockIssuedDuringPeriodSharesNewIssues
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261,958us-gaap_StockIssuedDuringPeriodSharesNewIssues
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| Share Conversion, Shares |
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(246,000)samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
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(2,013,677)samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
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| Balance, Shares |
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4,520,413us-gaap_CommonStockSharesOutstanding
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4,464,617us-gaap_CommonStockSharesOutstanding
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4,520,413us-gaap_CommonStockSharesOutstanding
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Resale and Registration Rights Agreement
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| Class Of Stock [Line Items] |
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| Share Conversion, Shares |
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110,000samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_ConversionOfStockByUniqueDescriptionAxis
= samg_ResaleAndRegistrationRightsAgreementMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
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133,739samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_ConversionOfStockByUniqueDescriptionAxis
= samg_ResaleAndRegistrationRightsAgreementMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
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| May 2014 |
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| Class Of Stock [Line Items] |
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| Stock repurchased/surrendered and cancelled , transaction date |
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May 01, 2014
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| Common stock repurchased/surrendered and cancelled |
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(5,893)us-gaap_StockRepurchasedDuringPeriodShares
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
/ us-gaap_TransactionTypeAxis
= samg_MayTwoThousandAndFourteenMember
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| Q3 2014 |
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| Class Of Stock [Line Items] |
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| Common stock conversion date |
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Sep. 30, 2014
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| Q3 2014 | Resale and Registration Rights Agreement |
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| Class Of Stock [Line Items] |
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| Share Conversion, Shares |
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(133,739)samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_ConversionOfStockByUniqueDescriptionAxis
= samg_ResaleAndRegistrationRightsAgreementMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
/ us-gaap_TransactionTypeAxis
= samg_SeptemberTwoThousandFourteenMember
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| Q4 2014 |
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| Class Of Stock [Line Items] |
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| Common stock conversion date |
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Dec. 31, 2014
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| Q4 2014 | Resale and Registration Rights Agreement |
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| Class Of Stock [Line Items] |
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| Share Conversion, Shares |
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(110,000)samg_StockIssuedDuringPeriodSharesConversionOfConvertibleShares
/ us-gaap_ConversionOfStockByUniqueDescriptionAxis
= samg_ResaleAndRegistrationRightsAgreementMember
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
/ us-gaap_TransactionTypeAxis
= samg_DecemberTwoThousandFourteenMember
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| December 2014 |
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| Class Of Stock [Line Items] |
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| Conversion of Class B common stock to Class A common stock, conversion date |
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Dec. 31, 2014
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| Common stock issued |
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60,000us-gaap_StockIssuedDuringPeriodSharesNewIssues
/ us-gaap_StatementClassOfStockAxis
= us-gaap_CommonClassBMember
/ us-gaap_TransactionTypeAxis
= samg_DecemberTwoZeroOneFourMember
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