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SECURITIES (Additional Information) (Detail) (One Corporate Debt Securities [Member], USD $)
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3 Months Ended |
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Mar. 31, 2015
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One Corporate Debt Securities [Member]
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| Available-for-sale Debt Securities Gross Unrealized Gain |
$ 29,000us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedGain / invest_InvestmentAxis = sfbs_OneCorporateDebtSecuritiesMember |
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- Definition
Amount of unrealized gain before deducting unrealized loss on investments in debt securities classified as available-for-sale securities. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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