XML 30 R52.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 | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Dec. 31, 2014
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | $ 4,585 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 | [1] | $ 1,791 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 | [1] |
Performing TDRs [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 36,423 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 36,983 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Commercial Real Estate [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 16,722 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 16,939 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Commercial and Industrial [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 7,988 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 8,074 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Commercial Construction [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 5,724 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 5,736 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Residential Mortgage [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 2,507 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 2,839 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Home Equity [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 3,438 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 3,342 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Performing TDRs [Member] | Installment and Other Consumer [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 44 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember |  |  |  | 53 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_AccruingTdrsMember
Nonperforming TDRs [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 9,916 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 5,436 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Commercial Real Estate [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 5,030 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 2,180 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Commercial and Industrial [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 1,772 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 356 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Commercial Construction [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 1,973 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 1,869 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Residential Mortgage [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 625 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 459 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Home Equity [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 510 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 562 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Nonperforming TDRs [Member] | Installment and Other Consumer [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 6 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember |  |  |  | 10 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = stba_NonaccruingTdrsMember
Total TDRs [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 46,339 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 42,419 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Commercial Real Estate [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 21,752 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 19,119 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Commercial and Industrial [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 9,760 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 8,430 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Commercial Construction [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 7,697 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 7,605 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Residential Mortgage [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 3,132 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 3,298 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Home Equity [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | 3,948 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | 3,904 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
Total TDRs [Member] | Installment and Other Consumer [Member] |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |
Restructured loans | $ 50 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember |  |  |  | $ 63 us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2 / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember / us-gaap_FinancingReceivableTroubledDebtRestructuringAxis = us-gaap_FinanceReceivablesMember
[1] | Excludes loans that were fully paid off or fully charged-off by period end. The pre-modification balance represents the balance outstanding prior to modification. The post-modification balance represents the outstanding balance at period end.

X
- Details
Name: | us-gaap_FinancingReceivableModificationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Post-modification amount of investment in financing receivables modified by troubled debt restructurings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_FinancingReceivableTroubledDebtRestructuringAxis=stba_AccruingTdrsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableTroubledDebtRestructuringAxis=stba_NonaccruingTdrsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableTroubledDebtRestructuringAxis=us-gaap_FinanceReceivablesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |