Annual report pursuant to Section 13 and 15(d)

DEBT SECURITIES (Additional Information) (Detail)

v2.4.1.9
DEBT SECURITIES (Additional Information) (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Description For Unrealized Loss Position 46 of the Company’s 707 debt securities were in an unrealized loss position for more than 12 months.  
Carrying Value Of Investment Securities Pledged $ 230,600,000sfbs_CarryingValueOfInvestmentSecuritiesPledged $ 200,900,000sfbs_CarryingValueOfInvestmentSecuritiesPledged
Federal Home Loan Bank Of Atlanta Stock [Member]    
Restricted Investments 3,200,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_FederalHomeLoanBankOfAtlantaStockMember 		3,500,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_FederalHomeLoanBankOfAtlantaStockMember
First National Bankers Bank Stock [Member]    
Restricted Investments 250,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_FirstNationalBankersBankStockMember 		250,000,000,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_FirstNationalBankersBankStockMember
CRA-Qualified Mutual Fund [Member]    
Restricted Investments $ 503,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_CraQualifiedMutualFundMember 		$ 493,000us-gaap_RestrictedInvestments
/ us-gaap_InvestmentTypeAxis
= sfbs_CraQualifiedMutualFundMember