XML 44 R35.htm IDEA: XBRL DOCUMENT
v3.23.1

Loans and Allowance for Credit Losses - Narrative (Details) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2023 USD ($) loan | Dec. 31, 2022 USD ($) loan
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Unearned income | $ 7.4 | $ 7.5
Purchase accounting fair value adjustments | $ 4.4 | $ 4.7
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status | 6 months |
Number of troubled debt restructuring loans returned to accruing status | loan |  | 1
Reclassified to accruing status |  | $ 0.2
Number of commitments to lend additional funds on TDRs | loan |  | 16
Commitments to lend additional funds on TDRs |  | $ 0.4
Default |  |
Financing Receivable, Allowance for Credit Loss [Line Items] |  |
Number of defaulted TDRs that were restructured within the last twelve months prior to defaulting | loan | 0 |

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: | 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 Status + References No definition available. + Details
Name: | stba_FinancialReceivableTroubleDebtRestructuringReclassifiedToAccruingStatus
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 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 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 Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 326 -SubTopic 20 -Name Accounting Standards Codification -Section 50 -Paragraph 13 -Publisher FASB -URI https://asc.fasb.org//1943274/2147479319/326-20-50-13 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-K (SK) -Number 229 -Section 1405 -Paragraph c -Publisher SEC + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
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 -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 34 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-34 + Details
Name: | us-gaap_FinancingReceivableModificationsSubsequentDefaultNumberOfContracts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of unamortized loan commitment, origination, and other costs (fees) on financing receivable recognized as adjustment to yield. Excludes financing receivable covered under loss sharing agreement. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 4 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481962/310-10-50-4 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 310 -SubTopic 20 -Name Accounting Standards Codification -Section 45 -Paragraph 1 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481598/310-20-45-1 Reference 3: http://www.xbrl.org/2003/role/recommendedDisclosureRef -Name Accounting Standards Codification -Section 50 -Paragraph 3 -SubTopic 20 -Topic 310 -Publisher FASB -URI https://asc.fasb.org//1943274/2147481569/310-20-50-3 + Details
Name: | us-gaap_FinancingReceivableUnamortizedLoanFeeCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_InternalCreditAssessmentAxis=stba_DefaultMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |