XML 44 R77.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans and Loans Held for Sale - Restructured Loans for Periods Presented (Detail) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Financing Receivable, Modifications [Line Items]    
Restructured loans $ 4,777us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 $ 11,018us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Performing Financing Receivable [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 36,983us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 39,229us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 16,939us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 19,711us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Commercial and Industrial [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 8,074us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 7,521us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Commercial Construction [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 5,736us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 5,338us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Residential Mortgage [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 2,839us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 2,581us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Home Equity [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 3,342us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 3,924us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Performing Financing Receivable [Member] | Installment and Other Consumer [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 53us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember		 154us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_PerformingFinancingReceivableMember
Nonperforming Financing Receivable [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 5,436us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 10,067us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 2,180us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 3,898us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Commercial and Industrial [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 356us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 1,884us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Commercial Construction [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 1,869us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 2,708us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Residential Mortgage [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 459us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 1,356us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Home Equity [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 562us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 218us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Nonperforming Financing Receivable [Member] | Installment and Other Consumer [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 10us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember		 3us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_NonperformingFinancingReceivableMember
Financing Receivable [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 42,419us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 49,296us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Commercial Real Estate [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 19,119us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 23,609us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_CommercialRealEstateMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Commercial and Industrial [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 8,430us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 9,405us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialAndIndustrialMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Commercial Construction [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 7,605us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 8,046us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_CommercialConstructionMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Residential Mortgage [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 3,298us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 3,937us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_ResidentialMortgageMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Home Equity [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans 3,904us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 4,142us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= us-gaap_HomeEquityMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember
Financing Receivable [Member] | Installment and Other Consumer [Member]    
Financing Receivable, Modifications [Line Items]    
Restructured loans $ 63us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember		 $ 157us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
/ us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis
= stba_InstallmentAndOtherConsumerMember
/ us-gaap_FinancingReceivableTroubledDebtRestructuringAxis
= us-gaap_FinanceReceivablesMember