XML 68 R53.htm IDEA: XBRL DOCUMENT v2.4.1.9
Fair Value Measurements (Assets And Liabilities Recorded At Fair Value On A Nonrecurring Basis) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Residential mortgage loans held for sale $ 527us-gaap_LoansHeldForSaleFairValueDisclosure $ 321us-gaap_LoansHeldForSaleFairValueDisclosure
Collateral-dependent impaired loans 1,552smmf_ImpairedLoansFairValueDisclosure 15,292smmf_ImpairedLoansFairValueDisclosure
Foreclosed properties 26,869smmf_OtherRealEstateForeclosedAssets 33,833smmf_OtherRealEstateForeclosedAssets
Commercial [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 44smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
450smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Commercial real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 344smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
4,390smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Foreclosed properties 3,892smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
7,997smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Construction and development [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 852smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
7,346smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Foreclosed properties 20,952smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
22,982smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Residential real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 312smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
3,099smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Foreclosed properties 2,025smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
2,854smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Consumer [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans   7smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Fair Value, Level 1 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Residential mortgage loans held for sale 0us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
0us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
Fair Value, Level 1 [Member] | Commercial [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Fair Value, Level 1 [Member] | Commercial real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Fair Value, Level 1 [Member] | Construction and development [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Fair Value, Level 1 [Member] | Residential real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Fair Value, Level 1 [Member] | Consumer [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans   0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel1Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Fair Value, Level 2 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Residential mortgage loans held for sale 527us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
321us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Collateral-dependent impaired loans 1,508smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
8,879smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Foreclosed properties 26,758smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
32,216smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
Fair Value, Level 2 [Member] | Commercial [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
60smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Fair Value, Level 2 [Member] | Commercial real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 344smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
1,538smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Foreclosed properties 3,892smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
7,997smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Fair Value, Level 2 [Member] | Construction and development [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 852smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
6,430smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Foreclosed properties 20,841smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
21,365smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Fair Value, Level 2 [Member] | Residential real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 312smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
848smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Foreclosed properties 2,025smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
2,854smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Fair Value, Level 2 [Member] | Consumer [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans   3smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel2Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember
Fair Value, Level 3 [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Residential mortgage loans held for sale 0us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
0us-gaap_LoansHeldForSaleFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Collateral-dependent impaired loans 44smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
6,413smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Foreclosed properties 111smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
1,617smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
Fair Value, Level 3 [Member] | Commercial [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 44smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
390smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialLoanMember
Fair Value, Level 3 [Member] | Commercial real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
2,852smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstatePortfolioSegmentMember
Fair Value, Level 3 [Member] | Construction and development [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
916smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Foreclosed properties 111smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
1,617smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ConstructionAndDevelopmentFinancialReceivableMember
Fair Value, Level 3 [Member] | Residential real estate [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans 0smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
2,251smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Foreclosed properties 0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
0smmf_OtherRealEstateForeclosedAssets
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= smmf_ResidentialRealEstateFinancialReceivableMember
Fair Value, Level 3 [Member] | Consumer [Member]    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Collateral-dependent impaired loans   $ 4smmf_ImpairedLoansFairValueDisclosure
/ us-gaap_FairValueByFairValueHierarchyLevelAxis
= us-gaap_FairValueInputsLevel3Member
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ConsumerPortfolioSegmentMember