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Securities (Summary Of Amortized Cost, Unrealized Gains, Unrealized Losses And Estimated Fair Values) (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost $ 275,204us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 276,631us-gaap_AvailableForSaleSecuritiesAmortizedCost $ 279,511us-gaap_AvailableForSaleSecuritiesAmortizedCost
Available for sale securities, Unrealized Gains 7,732us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax 7,170us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax 4,820us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Available for sale securities, Unrealized Losses 801us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax 967us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax 2,466us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Available for sale securities, Estimated Fair Value 282,135smmf_AvailableForSaleSecuritiesFairValueDisclosure1 282,834smmf_AvailableForSaleSecuritiesFairValueDisclosure1 281,865smmf_AvailableForSaleSecuritiesFairValueDisclosure1
U S Government Corporations And Agencies Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 21,650us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 22,153us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 27,658us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Available for sale securities, Unrealized Gains 1,227us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 1,073us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 736us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Available for sale securities, Unrealized Losses 40us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 52us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 78us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Available for sale securities, Estimated Fair Value 22,837smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 23,174smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember		 28,316smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USGovernmentCorporationsAndAgenciesSecuritiesMember
Government Sponsored Agencies [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 153,904us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 147,951us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 142,644us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember
Available for sale securities, Unrealized Gains 3,412us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 2,599us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 2,230us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember
Available for sale securities, Unrealized Losses 501us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 773us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 1,060us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember
Available for sale securities, Estimated Fair Value 156,815smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 149,777smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember		 143,814smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_GovernmentSponsoredAgenciesMember
Nongovernment Sponsored Agencies [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 11,034us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 12,051us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 10,429us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember
Available for sale securities, Unrealized Gains 105us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 142us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 377us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember
Available for sale securities, Unrealized Losses 71us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 48us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 19us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember
Available for sale securities, Estimated Fair Value 11,068smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 12,145smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember		 10,787smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_NongovernmentSponsoredAgenciesMember
U S States And Political Subdivisions General Obligations [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 1,617us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 1,975us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 5,681us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available for sale securities, Unrealized Gains 34us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 2us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 7us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 33us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 209us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
Available for sale securities, Estimated Fair Value 1,651smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 1,944smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember		 5,479smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_USStatesAndPoliticalSubdivisionsMember
State and Policital Subdivisions Water and Sewer Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 1,969us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 1,976us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 2,389us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember
Available for sale securities, Unrealized Gains 21us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 14us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 8us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 7us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 60us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember
Available for sale securities, Estimated Fair Value 1,990smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 1,983smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember		 2,337smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_WaterAndSewerRevenuesMember
State and Political Subdivisions Lottery/Casino Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 3,084us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsLotteryandCasinoRevenuesMember		    
Available for sale securities, Unrealized Gains 9us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsLotteryandCasinoRevenuesMember		    
Available for sale securities, Unrealized Losses 28us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsLotteryandCasinoRevenuesMember		    
Available for sale securities, Estimated Fair Value 3,065smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsLotteryandCasinoRevenuesMember		    
State and Policital Subdivisions Other Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 1,697us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 4,696us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 3,021us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember
Available for sale securities, Unrealized Gains 67us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 73us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 2us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 106us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember
Available for sale securities, Estimated Fair Value 1,764smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 4,767smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember		 2,915smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_OtherRevenuesMember
Corporate Debt Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 6,675us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 3,776us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 3,977us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available for sale securities, Unrealized Gains 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 25us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available for sale securities, Unrealized Losses 10us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 4us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Available for sale securities, Estimated Fair Value 6,665smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 3,776smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember		 3,998smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_CorporateDebtSecuritiesMember
Taxable Debt Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 201,630us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 194,578us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 195,799us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember
Available for sale securities, Unrealized Gains 4,875us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 3,903us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 3,383us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember
Available for sale securities, Unrealized Losses 650us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 915us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 1,536us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember
Available for sale securities, Estimated Fair Value 205,855smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 197,566smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember		 197,646smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxableDebtSecuritiesMember
State and Political Subdivisions General Obligations [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 47,947us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 49,515us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 45,761us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember
Available for sale securities, Unrealized Gains 2,050us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 2,338us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 1,109us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember
Available for sale securities, Unrealized Losses 136us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 12us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 504us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember
Available for sale securities, Estimated Fair Value 49,861smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 51,841smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember		 46,366smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsGeneralObligationsMember
State and Political Subdivisions Water and Sewer Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 10,302us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 11,258us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 14,033us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember
Available for sale securities, Unrealized Gains 278us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 244us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 64us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember
Available for sale securities, Unrealized Losses 1us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 3us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 110us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember
Available for sale securities, Estimated Fair Value 10,579smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 11,499smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember		 13,987smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsWaterAndSewerRevenuesMember
State and Political Subdivisions Special Tax Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 2,272us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsSpecialTaxRevenuesMember		    
Available for sale securities, Unrealized Gains 53us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsSpecialTaxRevenuesMember		    
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsSpecialTaxRevenuesMember		    
Available for sale securities, Estimated Fair Value 2,325smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateandPoliticalSubdivisionsSpecialTaxRevenuesMember		    
State and Political Subdivisions Lease Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost   4,617us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember		 9,079us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember
Available for sale securities, Unrealized Gains   75us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember		 47us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember
Available for sale securities, Unrealized Losses   10us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember		 168us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember
Available for sale securities, Estimated Fair Value   4,682smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember		 8,958smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLeaseRevenuesMember
State and Political Subdivisions Lottery/casino Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 2,800us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 3,811us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 4,428us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember
Available for sale securities, Unrealized Gains 163us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 206us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 102us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 9us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 79us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember
Available for sale securities, Estimated Fair Value 2,963smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 4,008smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember		 4,451smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsLotteryCasinoRevenuesMember
State and Political Subdivisions Other Revenues [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 10,246us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 12,845us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 10,334us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember
Available for sale securities, Unrealized Gains 313us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 404us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 115us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember
Available for sale securities, Unrealized Losses 14us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 18us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 69us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember
Available for sale securities, Estimated Fair Value 10,545smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 13,231smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember		 10,380smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_StateAndPoliticalSubdivisionsOtherRevenuesMember
Tax Exempt Debt Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 73,567us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 82,046us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 83,635us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember
Available for sale securities, Unrealized Gains 2,857us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 3,267us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 1,437us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember
Available for sale securities, Unrealized Losses 151us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 52us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 930us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember
Available for sale securities, Estimated Fair Value 76,273smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 85,261smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember		 84,142smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= smmf_TaxExemptDebtSecuritiesMember
Equity Securities [Member]      
Schedule of Available-for-sale Securities [Line Items]      
Total Amortized Cost 7us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 7us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 77us-gaap_AvailableForSaleSecuritiesAmortizedCost
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available for sale securities, Unrealized Gains 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available for sale securities, Unrealized Losses 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 0us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember
Available for sale securities, Estimated Fair Value $ 7smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 $ 7smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember		 $ 77smmf_AvailableForSaleSecuritiesFairValueDisclosure1
/ us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis
= us-gaap_EquitySecuritiesMember