XML 101 R88.htm IDEA: XBRL DOCUMENT
v3.20.4

Allowance for Credit Losses - Loan Balances by Year of Origination and Performing and Nonperforming Status (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Jan. 01, 2020 | Dec. 31, 2019
--- | --- | --- | ---
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | $ 1,360,684 |  |
2019 | 1,214,746 |  |
2018 | 831,734 |  |
2017 | 565,201 |  |
2016 | 610,556 |  |
2015 and Prior | 1,572,826 |  |
Revolving | 1,041,199 |  |
Revolving-Term | 28,914 |  |
Total | 7,225,860 |  | $ 7,137,152
Performing TDRs |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 1,360,654 |  |
2019 | 1,196,491 |  |
2018 | 827,625 |  |
2017 | 543,253 |  |
2016 | 586,622 |  |
2015 and Prior | 1,496,135 |  |
Revolving | 1,040,544 |  |
Revolving-Term | 27,762 |  |
Total | 7,079,086 |  |
Nonperforming TDRs |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 30 |  |
2019 | 18,254 |  |
2018 | 4,108 |  |
2017 | 21,948 |  |
2016 | 23,934 |  |
2015 and Prior | 76,691 |  |
Revolving | 654 |  |
Revolving-Term | 1,153 |  |
Total | 146,774 |  |
Commercial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Total | 5,977,643 |  | 5,756,971
Commercial | Commercial real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 334,086 |  |
2019 | 476,203 |  |
2018 | 417,944 |  |
2017 | 320,140 |  |
2016 | 415,184 |  |
2015 and Prior | 780,560 |  |
Revolving | 47,830 |  |
Revolving-Term | 0 |  |
Total | 2,791,947 | $ 3,416,518 | 3,059,592
Commercial | Commercial and industrial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 457,828 |  |
2019 | 215,457 |  |
2018 | 145,290 |  |
2017 | 82,249 |  |
2016 | 28,488 |  |
2015 and Prior | 221,609 |  |
Revolving | 408,631 |  |
Revolving-Term | 0 |  |
Total | 1,559,552 | 1,720,833 | 1,480,529
Commercial | Commercial construction |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 132,813 |  |
2019 | 230,907 |  |
2018 | 63,535 |  |
2017 | 2,921 |  |
2016 | 6,346 |  |
2015 and Prior | 16,777 |  |
Revolving | 12,778 |  |
Revolving-Term | 0 |  |
Total | 466,077 | 375,445 | 370,060
Commercial | Business banking |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 296,357 |  |
2019 | 156,473 |  |
2018 | 128,250 |  |
2017 | 91,363 |  |
2016 | 82,202 |  |
2015 and Prior | 298,779 |  |
Revolving | 105,549 |  |
Revolving-Term | 1,094 |  |
Total | 1,160,067 | 0 | 846,790
Commercial | Performing TDRs | Commercial real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 334,086 |  |
2019 | 459,799 |  |
2018 | 417,944 |  |
2017 | 313,465 |  |
2016 | 394,972 |  |
2015 and Prior | 722,782 |  |
Revolving | 47,830 |  |
Revolving-Term | 0 |  |
Total | 2,690,879 |  |
Commercial | Performing TDRs | Commercial and industrial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 457,828 |  |
2019 | 214,144 |  |
2018 | 143,706 |  |
2017 | 69,411 |  |
2016 | 28,426 |  |
2015 and Prior | 220,701 |  |
Revolving | 408,350 |  |
Revolving-Term | 0 |  |
Total | 1,542,566 |  |
Commercial | Performing TDRs | Commercial construction |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 132,813 |  |
2019 | 230,907 |  |
2018 | 63,535 |  |
2017 | 2,921 |  |
2016 | 6,346 |  |
2015 and Prior | 16,393 |  |
Revolving | 12,778 |  |
Revolving-Term | 0 |  |
Total | 465,692 |  |
Commercial | Performing TDRs | Business banking |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 296,327 |  |
2019 | 156,164 |  |
2018 | 126,432 |  |
2017 | 90,414 |  |
2016 | 80,106 |  |
2015 and Prior | 286,970 |  |
Revolving | 105,494 |  |
Revolving-Term | 1,037 |  |
Total | 1,142,944 |  |
Commercial | Nonperforming TDRs | Commercial real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 0 |  |
2019 | 16,404 |  |
2018 | 0 |  |
2017 | 6,675 |  |
2016 | 20,212 |  |
2015 and Prior | 57,778 |  |
Revolving | 0 |  |
Revolving-Term | 0 |  |
Total | 101,070 |  |
Commercial | Nonperforming TDRs | Commercial and industrial |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 0 |  |
2019 | 1,313 |  |
2018 | 1,584 |  |
2017 | 12,838 |  |
2016 | 62 |  |
2015 and Prior | 908 |  |
Revolving | 281 |  |
Revolving-Term | 0 |  |
Total | 16,985 |  |
Commercial | Nonperforming TDRs | Commercial construction |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 0 |  |
2019 | 0 |  |
2018 | 0 |  |
2017 | 0 |  |
2016 | 0 |  |
2015 and Prior | 384 |  |
Revolving | 0 |  |
Revolving-Term | 0 |  |
Total | 384 |  |
Commercial | Nonperforming TDRs | Business banking |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 30 |  |
2019 | 309 |  |
2018 | 1,818 |  |
2017 | 949 |  |
2016 | 2,096 |  |
2015 and Prior | 11,809 |  |
Revolving | 55 |  |
Revolving-Term | 57 |  |
Total | 17,123 |  |
Consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Total | 1,248,217 |  | 1,380,181
Consumer | Commercial construction |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
Total |  |  | 8,390
Consumer | Consumer real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 120,736 |  |
2019 | 122,544 |  |
2018 | 69,931 |  |
2017 | 65,133 |  |
2016 | 76,254 |  |
2015 and Prior | 251,047 |  |
Revolving | 439,020 |  |
Revolving-Term | 22,667 |  |
Total | 1,167,332 | 1,545,323 | 1,295,207
Consumer | Other consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 18,864 |  |
2019 | 13,162 |  |
2018 | 6,784 |  |
2017 | 3,395 |  |
2016 | 2,082 |  |
2015 and Prior | 4,054 |  |
Revolving | 27,391 |  |
Revolving-Term | 5,153 |  |
Total | 80,885 | $ 79,033 | $ 84,974
Consumer | Performing TDRs | Consumer real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 120,736 |  |
2019 | 122,315 |  |
2018 | 69,225 |  |
2017 | 63,647 |  |
2016 | 74,690 |  |
2015 and Prior | 245,331 |  |
Revolving | 438,702 |  |
Revolving-Term | 21,572 |  |
Total | 1,156,216 |  |
Consumer | Performing TDRs | Other consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 18,864 |  |
2019 | 13,162 |  |
2018 | 6,784 |  |
2017 | 3,395 |  |
2016 | 2,082 |  |
2015 and Prior | 3,958 |  |
Revolving | 27,391 |  |
Revolving-Term | 5,153 |  |
Total | 80,789 |  |
Consumer | Nonperforming TDRs | Consumer real estate |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 0 |  |
2019 | 229 |  |
2018 | 706 |  |
2017 | 1,486 |  |
2016 | 1,564 |  |
2015 and Prior | 5,716 |  |
Revolving | 318 |  |
Revolving-Term | 1,096 |  |
Total | 11,116 |  |
Consumer | Nonperforming TDRs | Other consumer |  |  |
Financing Receivable, Credit Quality Indicator [Line Items] |  |  |
2020 | 0 |  |
2019 | 0 |  |
2018 | 0 |  |
2017 | 0 |  |
2016 | 0 |  |
2015 and Prior | 96 |  |
Revolving | 0 |  |
Revolving-Term | 0 |  |
Total | $ 96 |  |

X
- Definition Amount of financing receivable originated more than five years prior to current fiscal year. + 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 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedFiveOrMoreYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated four years prior to current fiscal year. + 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 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedFourYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in current fiscal year. + 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 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedInCurrentFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated in fiscal year prior to current fiscal year. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 Reference 2: 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 + Details
Name: | us-gaap_FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated three years prior to current fiscal year. + 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 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of financing receivable originated two years prior to current fiscal year. + 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 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 + Details
Name: | us-gaap_FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of financing receivable that can be withdrawn, repaid and redrawn. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 326 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL82919232-210447 Reference 2: 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 + Details
Name: | us-gaap_FinancingReceivableRevolving
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of revolving financing receivable converted to term loan. + 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 6A -URI http://asc.fasb.org/extlink&oid=121599337&loc=SL120270059-210447 + Details
Name: | us-gaap_FinancingReceivableRevolvingConvertedToTermLoan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

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