Annual report pursuant to Section 13 and 15(d)

DEBT SECURITIES (Investment Securities Continuous Unrealized Loss Position) (Detail)

v2.4.1.9
DEBT SECURITIES (Investment Securities Continuous Unrealized Loss Position) (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Gross Unrealized Losses $ (659)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses $ (2,269)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
Fair Value 48,516us-gaap_InvestmentsFairValueDisclosure 73,977us-gaap_InvestmentsFairValueDisclosure
U.S. Treasury and Government Sponsored Agencies [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember 		(41)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember 		5,854us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
Mortgage-Backed Securities [Member]    
Gross Unrealized Losses (331)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember 		(1,520)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value 17,751us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember 		28,056us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
State and Municipal Securities [Member]    
Gross Unrealized Losses (328)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember 		(682)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Fair Value 30,765us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember 		34,109us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Corporate Debt [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember 		(26)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember 		5,958us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
Less Than Twelve Months [Member]    
Gross Unrealized Losses (162)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		(1,526)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Fair Value 19,945us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		63,843us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Less Than Twelve Months [Member] | U.S. Treasury and Government Sponsored Agencies [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		(41)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		5,854us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Less Than Twelve Months [Member] | Mortgage-Backed Securities [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		(852)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		21,365us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Less Than Twelve Months [Member] | State and Municipal Securities [Member]    
Gross Unrealized Losses (162)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		(607)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Fair Value 19,945us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		30,666us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Less Than Twelve Months [Member] | Corporate Debt [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		(26)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember 		5,958us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_LessThanTwelveMonthsMember
Twelve Months Or More [Member]    
Gross Unrealized Losses (497)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		(743)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Fair Value 28,571us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		10,134us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Twelve Months Or More [Member] | U.S. Treasury and Government Sponsored Agencies [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Fair Value 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USTreasuryAndGovernmentMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Twelve Months Or More [Member] | Mortgage-Backed Securities [Member]    
Gross Unrealized Losses (331)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		(668)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Fair Value 17,751us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		6,691us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_MortgageBackedSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Twelve Months Or More [Member] | State and Municipal Securities [Member]    
Gross Unrealized Losses (166)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		(75)us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Fair Value 10,820us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		3,443us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Twelve Months Or More [Member] | Corporate Debt [Member]    
Gross Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		0us-gaap_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionLessThan12MonthsAggregateLosses
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember
Fair Value $ 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember 		$ 0us-gaap_InvestmentsFairValueDisclosure
/ us-gaap_GainLossOnInvestmentsByCategoryAxis
= us-gaap_CorporateDebtSecuritiesMember
/ us-gaap_StatementScenarioAxis
= sfbs_TwelveMonthsOrMoreMember