XML 59 R49.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Loans and Loans Held for Sale - Summary of Restructured Loans (Detail) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jun. 30, 2016 USD ($) tdr | Jun. 30, 2015 USD ($) tdr | Jun. 30, 2016 USD ($) tdr | Jun. 30, 2015 USD ($) tdr | Dec. 31, 2015 USD ($)
Receivables [Abstract] |  |  |  |  |  |
Loans Receivable Held-for-sale, Reconciliation to Cash Flow, Period Increase (Decrease) |  |  |  | $ 23,300 |  |
Gain on sale of credit card portfolio |  | $ 0 | $ 0 | $ 2,066 | $ 0 |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  |  | 6 months |  |
Restructured loans | [1] | $ 8,193 | $ 796 | $ 10,771 | $ 5,381 |
Number of troubled debt restructuring loans returned back to accruing status | tdr |  | 0 | 6 | 0 | 6 |
Amount of troubled debt restructuring loans returned back to accruing status |  |  | $ 300 |  | $ 300 |
Performing Financial Instruments |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | $ 20,598 |  | $ 23,955
Performing Financial Instruments | Commercial and Industrial |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 6,241 |  | 6,321
Performing Financial Instruments | Commercial Real Estate |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 4,263 |  | 6,822
Performing Financial Instruments | Commercial Construction |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 4,351 |  | 5,013
Performing Financial Instruments | Residential Mortgage |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 2,493 |  | 2,590
Performing Financial Instruments | Home Equity |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 3,225 |  | 3,184
Performing Financial Instruments | Installment and Other Consumer |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 25 |  | 25
Nonperforming Financial Instruments |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 15,028 |  | 7,659
Nonperforming Financial Instruments | Commercial and Industrial |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 2,535 |  | 1,570
Nonperforming Financial Instruments | Commercial Real Estate |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 4,369 |  | 3,548
Nonperforming Financial Instruments | Commercial Construction |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 2,820 |  | 1,265
Nonperforming Financial Instruments | Residential Mortgage |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 4,411 |  | 665
Nonperforming Financial Instruments | Home Equity |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 882 |  | 523
Nonperforming Financial Instruments | Installment and Other Consumer |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 11 |  | 88
Financing Receivable |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 35,626 |  | 31,614
Financing Receivable | Commercial and Industrial |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 8,776 |  | 7,891
Financing Receivable | Commercial Real Estate |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 8,632 |  | 10,370
Financing Receivable | Commercial Construction |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 7,171 |  | 6,278
Financing Receivable | Residential Mortgage |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 6,904 |  | 3,255
Financing Receivable | Home Equity |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | 4,107 |  | 3,707
Financing Receivable | Installment and Other Consumer |  |  |  |  |  |
Financing Receivable, Modifications [Line Items] |  |  |  |  |  |
Restructured loans |  |  |  | $ 36 |  | $ 113
[1] | (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
- Definition Financing Receivable Modification Post Modification Loans Removed From Nonaccrual Status + References No definition available. + Details
Name: | stba_FinancingReceivableModificationPostModificationLoansRemovedFromNonaccrualStatus
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of troubled debt restructuring loans returned back to accruing status. + References No definition available. + Details
Name: | stba_NumberOfTroubledDebtRestructuringLoansReturnedBackToAccruingStatus
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Threshold Period of Satisfactory Payments to Remove from Nonaccrual Status + References No definition available. + Details
Name: | stba_ThresholdPeriodofSatisfactoryPaymentstoRemovefromNonaccrualStatus
Namespace Prefix: | stba_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + 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=66008989&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The net gain (loss) resulting from a sale of loans, including adjustments to record loans classified as held-for-sale at the lower-of-cost-or-market and fair value adjustments to loan held for investment purposes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.3(a)) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.13(h)) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 + Details
Name: | us-gaap_GainLossOnSalesOfLoansNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount, after allowance for bad debt, of increase (decrease) in loan receivables held-for-sale that are not part of a disposal group. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=65884687&loc=d3e4428-111522 + Details
Name: | us-gaap_LoansReceivableHeldForSaleReconciliationToCashFlowPeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_ReceivablesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_PerformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_EquitySecuritiesByIndustryAxis=us-gaap_CommercialAndIndustrialSectorMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialMortgageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerBorrowerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancialInstrumentPerformanceStatusAxis=us-gaap_NonperformingFinancingReceivableMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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