XML 86 R70.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Loans and Loans Held for Sale - Additional Information (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2017 USD ($) loan | Dec. 31, 2016 USD ($) loan
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Unearned income on loans and leases receivable | $ 5,200 | $ 5,200
Net unamortized discount related to purchase accounting fair value adjustments | 2,800 | 7,100
Loans receivable, net | $ 5,765,934 | $ 5,615,212
Number of loan modified | loan | 15 |
Number of commitments to lend additional funds on TDRs | loan | 2 |
Commitment to lend additional funds on TDRs | $ 200 |
Number of TDRs returned back to accruing status | loan | 1 | 5
Financial receivable trouble debt restructuring reclassified to accruing trouble debt restructuring status | $ 2,000 | $ 900
Minimum period of loan payment defaults following restructure for TDRs to be in default | 90 days |
Number of defaulted TDRs that were restructured within twelve months prior to defaulting | loan | 0 | 0
Decrease in nonperforming assets | $ 18,900 |
Nonperforming assets | $ 24,407 | $ 43,314
Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Percentage of commercial loans in total portfolio loans | 78.00% | 78.00%
Loans recorded investment | $ 4,503,594 | $ 4,355,395
Commercial real estate |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | $ 2,685,994 | 2,498,476
Number of loan modified | loan | 5 |
Loans modified not considered to be troubled debt restructuring | $ 7,500 |
Commercial real estate | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans recorded investment | 2,685,994 | 2,498,476
Commercial and industrial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | $ 1,433,266 | 1,401,035
Number of loan modified | loan | 10 |
Loans modified not considered to be troubled debt restructuring | $ 10,800 |
Number of nonperforming, impaired loans paid off during the period | loan | 2 |
Balance of nonperforming, impaired loans paid off during the period | $ 10,500 |
Commercial and industrial | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans recorded investment | 1,433,266 | 1,401,035
Commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 384,334 | 455,884
Commercial construction | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans recorded investment | 384,334 | 455,884
Residential mortgage |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 698,774 | 701,982
Consumer construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | $ 4,551 | $ 5,906
CRE and Commercial Construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Out-of-state exposure of combined portfolio | 5.20% | 5.20%
Percentage of total loans out-of-state | 2.80% | 2.70%
CRE and Commercial Construction | Commercial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans recorded investment | $ 3,100,000 | $ 3,000,000
Combined percentage of commercial real estate and commercial construction in total commercial loans | 68.00% | 68.00%
Combined percentage of commercial real estate and commercial construction in total portfolio loans | 53.00% | 53.00%
Concentration risk percentage | 0.00% | 0.00%
Maximum concentration of commercial real estate and commercial construction portfolio in loans | 14.00% | 14.00%
Integrity Bancshares, Inc. |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | $ 387,000 | $ 543,000
Integrity Bancshares, Inc. | Commercial real estate |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 209,000 | 273,000
Integrity Bancshares, Inc. | Commercial and industrial |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 92,100 | 141,000
Integrity Bancshares, Inc. | Commercial construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 11,100 | 33,000
Integrity Bancshares, Inc. | Residential mortgage |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | 57,500 | 74,000
Integrity Bancshares, Inc. | Home Equity, Installment and Other Consumer Construction |  |
Accounts, Notes, Loans and Financing Receivable [Line Items] |  |
Loans receivable, net | $ 17,300 | $ 22,000

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, Nonaccrual Status and Impaired Paid Off During the Period, Number of Contracts + References No definition available. + Details
Name: | stba_FinancingReceivableNonaccrualStatusandImpairedPaidOffDuringthePeriodNumberofContracts
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Financing Receivable, Nonaccrual Status and Impaired Paid Off During the Period, Recorded Investment + References No definition available. + Details
Name: | stba_FinancingReceivableNonaccrualStatusandImpairedPaidOffDuringthePeriodRecordedInvestment
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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 Loans modified not considered to be troubled debt restructuring. + References No definition available. + Details
Name: | stba_LoansModifiedNotConsideredToBeTroubledDebtRestructuring
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 + References No definition available. + Details
Name: | stba_NetLoansOutOfStatePercentage
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 Loans Modified Not Considered To Be Troubled Debt Restructuring + References No definition available. + Details
Name: | stba_NumberOfLoansModifiedNotConsideredToBeTroubledDebtRestructuring
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 Number of 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 Whiting Twelve Months Prior to Defaulting + References No definition available. + Details
Name: | stba_NumberofDefaultedTroubledDebtRestructuringLoansRestructuredWhitingTwelveMonthsPriortoDefaulting
Namespace Prefix: | stba_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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 Total remaining unamortized or unaccreted amounts of premiums, discounts, and intangible assets, in years subsequent to the year of acquisition, when the total amounts of remaining discounts, premiums, and intangible assets exceed 30 percent of stockholders' equity. + References No definition available. + Details
Name: | us-gaap_BusinessAcquisitionsPurchasePriceAllocationSubsequentYearsRemainingAdjustments
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 18 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6351-108592 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13531-108611 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 275 -SubTopic 10 -Section 50 -Paragraph 20 -URI http://asc.fasb.org/extlink&oid=84177426&loc=d3e6404-108592 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 21 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=77997519&loc=d3e13537-108611 + 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://www.xbrl.org/2003/role/presentationRef -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 Reference 2: http://www.xbrl.org/2003/role/presentationRef -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 3: http://www.xbrl.org/2003/role/presentationRef -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 4: http://www.xbrl.org/2003/role/presentationRef -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 + 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://www.xbrl.org/2003/role/presentationRef -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 Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03.7(a)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
Name: | us-gaap_LoansReceivableNet
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_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=us-gaap_ResidentialMortgageMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=stba_ConsumerConstructionMember
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_BusinessAcquisitionAxis=stba_IntegrityBancsharesInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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