XML 94 R81.htm IDEA: XBRL DOCUMENT
v3.20.4

Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands |  |  | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | ---
Dec. 31, 2020 USD ($) loan | Dec. 31, 2019 USD ($) loan | Dec. 31, 2020 USD ($) loan | Sep. 30, 2020 USD ($) | Mar. 31, 2020 USD ($) | Dec. 31, 2020 USD ($) loan | Dec. 31, 2019 USD ($) loan | Jan. 01, 2020 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Unearned income | $ 16,000 | $ 4,600 | $ 16,000 |  |  | $ 16,000 | $ 4,600 |
Purchase accounting fair value adjustments | 8,600 | 12,300 |  |  |  |  |  |
Portfolio loans, net | 7,108,248 | 7,074,928 | 7,108,248 |  |  | 7,108,248 | 7,074,928 | $ 7,074,928
Portfolio loans, net of unearned income | $ 7,225,860 | $ 7,137,152 | $ 7,225,860 |  |  | 7,225,860 | 7,137,152 |
Restructured loans |  |  |  |  |  | $ 22,650 | $ 32,206 |
Number of commitments to lend additional funds | loan | 20 | 24 | 20 |  |  | 20 | 24 |
Commitment to lend additional funds | $ 800 | $ 4,600 | $ 800 |  |  | $ 800 | $ 4,600 |
Number of TDRs returned back to accruing status | loan |  |  |  |  |  | 1 | 6 |
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status |  |  |  |  |  | $ 100 | $ 500 |
Minimum period of loan payment defaults following restructure for TDRs to be in default (in days) |  |  |  |  |  | 90 days |  |
Number of TDRs defaulted that were restructured within the last 12 months prior to defaulting | loan |  |  |  |  |  | 6 | 0 |
Financial receivable defaulted trouble debt restructuring loans restructured within twelve months prior to defaulting |  |  |  |  |  | $ 11,800 |  |
Increase in nonperforming assets |  |  |  |  |  | 91,300 |  |
Nonperforming assets | $ 148,929 | $ 57,582 | $ 148,929 |  |  | $ 148,929 | $ 57,582 |
CARES Act, Paycheck Protection Program Loans |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Number of modified loans | loan |  |  |  |  |  | 52 |  |
Modified Loans |  |  |  |  |  | $ 195,600 |  |
Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Percentage of commercial loans in total portfolio loans | 79.00% | 77.00% | 79.00% |  |  | 79.00% | 77.00% |
Portfolio loans, net of unearned income | $ 5,977,643 | $ 5,756,971 | $ 5,977,643 |  |  | $ 5,977,643 | $ 5,756,971 |
CARES Act, Paycheck Protection Program Loans |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  | 195,600 |  |
CARES Act, Paycheck Protection Program Loans | COVID-19 |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Portfolio loans, net | 465,000 |  | 465,000 |  |  | 465,000 |  |
CARES Act, Paycheck Protection Program Loans | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Portfolio loans, net | 465,000 |  | 465,000 |  |  | 465,000 |  |
CRE and Commercial Construction | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Portfolio loans, net of unearned income | $ 3,700,000 | $ 3,800,000 | $ 3,700,000 |  |  | $ 3,700,000 | $ 3,800,000 |
Combined percentage of commercial real estate and commercial construction in total commercial loans | 66.00% | 69.00% | 66.00% |  |  | 66.00% | 69.00% |
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 51.00% | 53.00% | 51.00% |  |  | 51.00% | 53.00% |
Concentration risk percentage |  |  |  |  |  | 0.00% | 0.00% |
Maximum concentration of commercial real estate and commercial construction portfolio in loans | 15.00% | 11.00% | 15.00% |  |  | 15.00% | 11.00% |
Out-of-state exposure of combined portfolio | 5.90% | 5.40% | 5.90% |  |  | 5.90% | 5.40% |
Percentage of total loans out-of-state excluding contiguous states | 3.00% | 2.90% | 3.00% |  |  | 3.00% | 2.90% |
Commercial real estate | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Portfolio loans, net of unearned income | $ 2,791,947 | $ 3,059,592 | $ 2,791,947 |  |  | $ 2,791,947 | $ 3,059,592 | 3,416,518
Restructured loans |  |  |  |  |  | 4,791 | 25,159 |
Commercial and industrial | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Portfolio loans, net of unearned income | 1,559,552 | $ 1,480,529 | 1,559,552 |  |  | 1,559,552 | 1,480,529 | $ 1,720,833
Restructured loans |  |  |  |  |  | 13,716 | $ 5,661 |
Nonperforming TDRs | Commercial real estate | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  | $ 21,300 |  |  |
Amount charged down |  |  |  | $ 10,000 |  |  |  |
Outstanding balance after charge down |  |  |  | $ 11,300 |  |  |  |
Nonperforming TDRs | Commercial real estate | Commercial | Customer one |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  | 11,300 |  |
Nonperforming TDRs | Commercial real estate | Commercial | Customer two |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  | 6,700 |  |
Nonperforming TDRs | Commercial real estate | Commercial | Hotel | COVID-19 |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  | 56,300 |  |  |  |  |
Nonperforming TDRs | Commercial real estate | Commercial | Customer fraud |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  |  |  |  | 5,900 |  |
Nonperforming TDRs | Commercial and industrial | Commercial |  |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |  |
Restructured loans |  |  | 11,200 |  |  | 15,100 |  |
Amount charged down |  |  | 1,600 |  |  |  |  |
Outstanding balance after charge down | $ 9,600 |  | $ 9,600 |  |  | $ 9,600 |  |

X
- Definition Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Acquired Receivable, Fair Value + References No definition available. + Details
Name: | stba_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentAcquiredReceivableFairValue
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Combined percentage of commercial real estate and commercial construction in commercial loans. + References No definition available. + Details
Name: | stba_CombinedPercentageOfCommercialRealEstateAndCommercialConstructionInCommercialLoans
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Combined percentage of commercial real estate and commercial construction in portfolio loans. + References No definition available. + Details
Name: | stba_CombinedPercentageOfCommercialRealEstateAndCommercialConstructionInPortfolioLoans
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Commitment To Lend Additional Funds + References No definition available. + Details
Name: | stba_CommitmentToLendAdditionalFunds
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status. + References No definition available. + Details
Name: | stba_FinancialReceivableTroubleDebtRestructuringReclassifiedToAccruingTroubleDebtRestructuringStatus
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Financing Receivable, Non-TDR Modifications, Number Of Contracts + References No definition available. + Details
Name: | stba_FinancingReceivableNonTDRModificationsNumberOfContracts
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Non-TDR Restructuring, Postmodification + References No definition available. + Details
Name: | stba_FinancingReceivableNonTDRRestructuringPostmodification
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Financing Receivables, Impaired, Troubled Debt Restructuring, After Write-Down + References No definition available. + Details
Name: | stba_FinancingReceivablesImpairedTroubledDebtRestructuringAfterWriteDown
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Increase (Decrease) in Net Nonperforming Assets + References No definition available. + Details
Name: | stba_IncreaseDecreaseinNetNonperformingAssets
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Maximum concentration of commercial real estate and commercial construction portfolio in loans. + References No definition available. + Details
Name: | stba_MaximumConcentrationOfCommercialRealEstateAndCommercialConstructionPortfolioInLoans
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Net loans out of state percentage excluding contiguous states. + References No definition available. + Details
Name: | stba_NetLoansOutOfStatePercentageExcludingContiguousStates
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Net nonperforming assets. + References No definition available. + Details
Name: | stba_NetNonperformingAssets
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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 Commitment To Lend Additional Funds + References No definition available. + Details
Name: | stba_NumberofCommitmentToLendAdditionalFunds
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Out of state exposure of combined portfolio. + References No definition available. + Details
Name: | stba_OutOfStateExposureOfCombinedPortfolio
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Percentage of commercial loans in portfolio loans. + References No definition available. + Details
Name: | stba_PercentageOfCommercialLoansInPortfolioLoans
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Period of loans in default treated as troubled debt restructuring. + References No definition available. + Details
Name: | stba_PeriodOfLoansInDefaultTreatedAsTroubledDebtRestructuring
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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 42 -URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e9054-108599 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6351-108592 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13531-108611 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=121572278&loc=d3e13537-108611 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=99393423&loc=d3e6404-108592 + Details
Name: | us-gaap_ConcentrationRiskPercentage1
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, after troubled debt restructuring, of modified financing receivable. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 33 -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953676-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of financing receivable contracts modified as troubled debt restructuring within previous 12 months, with subsequent payment default. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of financing receivable modified as troubled debt restructuring within previous 12 months, with subsequent payment default. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 34 -Subparagraph (a)(2) -URI http://asc.fasb.org/extlink&oid=121611835&loc=SL6953682-111524 + Details
Name: | us-gaap_FinancingReceivableModificationsSubsequentDefaultRecordedInvestment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of unamortized loan commitment, origination, and other fees (costs) on financing receivable. Excludes financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6378536&loc=d3e10092-111533 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121611835&loc=d3e5074-111524 Reference 3: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=84159169&loc=d3e10152-111534 + Details
Name: | us-gaap_FinancingReceivableUnamortizedLoanFeeCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Reflects the amount of the write-down related to a troubled debt restructuring. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 40 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=121585226&loc=d3e18845-111554 + Details
Name: | us-gaap_FinancingReceivablesImpairedTroubledDebtRestructuringWriteDown
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, before allowance for credit loss, of financing receivable. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 79 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922352-210448 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919230-210447 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 55 -Paragraph 80 -URI http://asc.fasb.org/extlink&oid=121647567&loc=SL82922355-210448 + Details
Name: | us-gaap_NotesReceivableGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919230-210447 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(3)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522 + Details
Name: | us-gaap_NotesReceivableNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_LoanRestructuringModificationNameAxis=stba_PaycheckProtectionProgramLoanCARESActMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

X
- Details
Name: | us-gaap_UnusualOrInfrequentItemAxis=stba_COVID19Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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

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

X
- Details
Name: | srt_MajorCustomersAxis=stba_CustomerOneMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_MajorCustomersAxis=stba_CustomerTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_CollateralAxis=srt_HotelMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_LoanRestructuringModificationNameAxis=stba_CustomerFraudMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |