XML 10 R52.htm IDEA: XBRL DOCUMENT
v3.20.1

Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Mar. 31, 2020 USD ($) loan | Dec. 31, 2019 USD ($) | Mar. 31, 2020 USD ($) note loan | Mar. 31, 2019 USD ($) loan | Dec. 31, 2019 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Loans, net of unearned income |  | $ 5,000 | $ 4,600 | $ 5,000 |  |  | $ 4,600
Purchase accounting fair value adjustments |  | $ 10,900 | $ 12,300 |  |  |  |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  |  | 6 months |  |  |
Restructured loans | [1] |  |  | $ 8,297 | [2] | $ 5,499 |
Number of troubled debt restructuring loans returned to accruing status | loan |  |  |  | 0 |  | 3 |
Amount of trouble debt restructuring loans returned to accruing status |  |  |  |  |  | $ 1,700 |
Number of commitments to lend additional funds on TDRs | loan |  | 20 |  | 20 |  |  |
Commitments to lend additional funds on TDRs |  | $ 2,300 |  | $ 2,300 |  |  |
Minimum period of loan payment defaults following restructure for TDRs to be in default |  |  |  | 90 days |  |  |
Number of defaulted TDRs that were restructured within the last twelve months prior to defaulting | loan |  |  |  | 11 |  | 0 |
Amount of defaulted TDRs that were restructured within the last twelve months prior to defaulting |  |  |  | $ 21,100 |  |  |
Number of notes related to individual customer resulting in an increase in defaulted troubled debt restructuring loans due to Covid-19 | note |  |  |  | 5 |  |  |
Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Percentage of commercial loans in total portfolio loans |  | 77.60% | 77.20% | 77.60% |  |  | 77.20%
Commercial loans |  |  | $ 5,512,796 |  |  |  | $ 5,512,796
Commercial real estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Restructured loans | [1] |  |  | $ 2,210 |  |  |
Commercial real estate | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loans |  |  | 3,416,518 |  |  |  | 3,416,518
CRE and commercial construction | Commercial |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Commercial loans |  | $ 3,800,000 | $ 3,800,000 | $ 3,800,000 |  |  | $ 3,800,000
Combined percentage of commercial real estate and commercial construction in total commercial loans |  | 68.30% | 68.80% | 68.30% |  |  | 68.80%
Combined percentage of commercial real estate and commercial construction in total portfolio loans |  | 53.00% | 53.10% | 53.00% |  |  | 53.10%
Concentration risk percentage of commercial real estate and commercial construction |  |  |  | 0.00% |  |  | 0.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans (in excess of) |  | 13.60% | 11.00% | 13.60% |  |  | 11.00%
Out of market exposure of combined portfolio (percent) |  | 5.40% | 5.40% | 5.40% |  |  | 5.40%
Percentage of total loans out-of-state excluding contiguous states |  | 2.80% | 2.90% | 2.80% |  |  | 2.90%
Nonperforming TDRs | Commercial real estate |  |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |  |
Restructured loans |  |  |  | $ 20,900 |  |  |
[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.
[2] | Refer to Note 1, Basis of Presentation for details of reclassification of our portfolio segments related to the adoption of ASU 2016-13 Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instrument.

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 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 Number Of Notes Related To Individual Customer Resulting In An Increase In Defaulted Troubled Debt Restructuring Loans Due To Covid-19 + References No definition available. + Details
Name: | stba_NumberOfNotesRelatedToIndividualCustomerResultingInAnIncreaseInDefaultedTroubledDebtRestructuringLoansDueToCovid19
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
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 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 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_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://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 2: 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=118260190&loc=d3e13531-108611 Reference 3: 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=118260190&loc=d3e13537-108611 Reference 4: 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=118936363&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=118936363&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=118936363&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 deferred interest and fee income, unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of acquired loans. Excludes amounts for loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 30 -Section 50 -Paragraph 4 -Subparagraph (a)(4) -URI http://asc.fasb.org/extlink&oid=84165051&loc=d3e45377-112738 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=118936363&loc=d3e5074-111524 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -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_LoansAndLeasesReceivableDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=118952595&loc=d3e4428-111522 + Details
Name: | us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
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_CommercialRealEstateAndCommercialConstructionMember
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: |