XML 54 R44.htm IDEA: XBRL DOCUMENT
v3.10.0.1

Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands | 3 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
Jun. 30, 2018 USD ($) loan | Jun. 30, 2017 USD ($) loan | Jun. 30, 2018 USD ($) loan | Jun. 30, 2017 USD ($) loan | Dec. 31, 2017 USD ($) | Mar. 31, 2018 Property
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Change-off arising from participation loan agreement | $ 8,632 | $ 5,822 | $ 10,076 | $ 8,763 |  |
Loans, net of unearned income | $ 5,400 |  | $ 5,400 |  | $ 5,200 |
Threshold period of satisfactory performance for troubled debt restructuring to be restored to accruing status |  |  | 6 months |  |  |
Number of troubled debt restructuring loans returned back to accruing status | loan | 0 | 1 | 0 | 1 |  |
Number of commitments to lend additional funds on TDRs | loan | 7 |  | 7 |  |  |
Commitments to lend additional funds on TDRs | $ 5,600 |  | $ 5,600 |  |  |
Minimum period of loan payment defaults following restructure for TDRs to be in default |  |  | 90 days |  |  |
Number of defaulted troubled debt restructuring loans restructured within twelve months prior to defaulting | loan | 0 | 0 | 0 | 0 |  |
Amount of defaulted troubled debt restructuring loans restructured within twelve months prior to defaulting |  | $ 2,000 |  | $ 2,000 |  |
Land |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Increase in other real estate |  |  | $ 2,500 |  |  |
Other real estate owned, number | Property |  |  |  |  |  | 2
Commercial |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Percentage of commercial loans in total portfolio loans | 79.00% |  | 79.00% |  | 78.00% |
Commercial loans | $ 4,544,006 |  | $ 4,544,006 |  | $ 4,503,594 |
Other consumer |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Change-off arising from participation loan agreement | 414 | $ 370 | 872 | $ 804 |  |
Commercial real estate and commercial construction | Commercial |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Commercial loans | $ 3,100,000 |  | $ 3,100,000 |  | $ 3,100,000 |
Combined percentage of commercial real estate and commercial construction in total commercial loans | 68.00% |  | 68.00% |  | 68.00% |
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 53.00% |  | 53.00% |  | 53.00% |
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) | 13.00% |  | 13.00% |  | 14.00% |
Out of market exposure of combined portfolio (percent) | 5.30% |  | 5.30% |  | 5.20% |
Percentage of total loans out-of-state excluding contiguous states | 2.80% |  | 2.80% |  | 2.80% |
Vehicles and Equipment Liens | Other consumer |  |  |  |  |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |  |  |  |  |
Change-off arising from participation loan agreement | $ 5,200 |  | $ 5,200 |  |  |

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 Financing Receivable, Modifications, Post-Modification Loans Removed From Nonaccrual Status + References No definition available. + Details
Name: | stba_FinancingReceivableModificationsPostModificationLoansRemovedFromNonaccrualStatus
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 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 Number of Defaulted Troubled Debt Restructuring Loans Restructured Within Twelve Months Prior to Defaulting + References No definition available. + Details
Name: | stba_NumberofDefaultedTroubledDebtRestructuringLoansRestructuredWithinTwelveMonthsPriortoDefaulting
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Other Real Estate, Number + References No definition available. + Details
Name: | stba_OtherRealEstateNumber
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 Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 Reference 2: 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(d)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_AllowanceForLoanAndLeaseLossesWriteOffs
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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=109250915&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=109250915&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 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=84173941&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=82891408&loc=d3e4428-111522 + Details
Name: | us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Change in carrying amount of other real estate not separately disclosed. The change includes for example, but is not limited to, additions, improvements, disposals and valuation adjustments. + References No definition available. + Details
Name: | us-gaap_OtherRealEstatePeriodIncreaseDecrease
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_MajorPropertyClassAxis=us-gaap_LandMember
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_OtherConsumerMember
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_CollateralAxis=stba_AutomobilesandEquipmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |