Quarterly report pursuant to Section 13 or 15(d)

EMPLOYEE AND DIRECTOR BENEFITS (Additional Information) (Detail)

v2.4.1.9
EMPLOYEE AND DIRECTOR BENEFITS (Additional Information) (Detail) (USD $)
3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Share based compensation $ 301,000us-gaap_ShareBasedCompensation $ 1,020,000us-gaap_ShareBasedCompensation
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value $ 7.61us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue $ 2.95us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized 1,700,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized  
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition 2 years 2 months 12 days  
Non Routine Expenses 703,000sfbs_NonRoutineExpenses  
Restricted Stock [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized $ 775,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition 1 year 6 months  
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures, Total 239,588us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures
/ us-gaap_AwardTypeAxis
= us-gaap_RestrictedStockMember
 
Plan 2005 [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares available for grant 3,075,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= sfbs_Plan2005Member
 
Plan 2009 [Member]    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Shares available for grant 2,775,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_PlanNameAxis
= sfbs_Plan2009Member