Annual report pursuant to Section 13 and 15(d)

DEBT SECURITIES (Amortized Cost And Fair Value Of Contractual Securities) (Detail)

v2.4.1.9
DEBT SECURITIES (Amortized Cost And Fair Value Of Contractual Securities) (Detail) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Available-for-sale    
Amortized Cost $ 291,403us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 259,734us-gaap_AvailableForSaleSecuritiesAmortizedCost
Fair Value 298,310us-gaap_AvailableForSaleSecurities 265,728us-gaap_AvailableForSaleSecurities
Held-to-maturity    
Amortized Cost 29,355us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment 32,274us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
Fair Value 29,974us-gaap_HeldToMaturitySecuritiesFairValue 31,315us-gaap_HeldToMaturitySecuritiesFairValue
Less than one year [Member]    
Available-for-sale    
Amortized Cost 16,944us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_DueWithinOneYearMember
5,659us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_DueWithinOneYearMember
Fair Value 17,246us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_DueWithinOneYearMember
5,717us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_DueWithinOneYearMember
One year to five years [Member]    
Available-for-sale    
Amortized Cost 121,591us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_DueFromOneToFiveYearsMember
102,535us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_DueFromOneToFiveYearsMember
Fair Value 123,962us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_DueFromOneToFiveYearsMember
104,887us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_DueFromOneToFiveYearsMember
Five years to ten years [Member]    
Available-for-sale    
Amortized Cost 60,079us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
65,174us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
Fair Value 61,221us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
66,229us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
Held-to-maturity    
Amortized Cost 298us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
0us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
Fair Value 325us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
0us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= sfbs_FiveYearsToTenYearsMember
More than Ten years [Member]    
Available-for-sale    
Amortized Cost 350us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
1,094us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
Fair Value 358us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
1,147us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
Held-to-maturity    
Amortized Cost 5,253us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
5,544us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
Fair Value 5,716us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
5,741us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= sfbs_MoreThanTenYearsMember
Mortgage-backed securities [Member]    
Available-for-sale    
Amortized Cost 92,439us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
85,272us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value 95,523us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
87,748us-gaap_AvailableForSaleSecurities
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
Held-to-maturity    
Amortized Cost 23,804us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
26,730us-gaap_HeldToMaturitySecuritiesAmortizedCostBeforeOtherThanTemporaryImpairment
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
Fair Value $ 23,933us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember
$ 25,574us-gaap_HeldToMaturitySecuritiesFairValue
/ us-gaap_StatementScenarioAxis
= us-gaap_MortgageBackedSecuritiesMember