XML 21 R57.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Allowance for Loan Losses - Recorded Investment in Commercial Loan Classes by Internally Assigned Risk Ratings (Detail) (USD $) In Thousands, unless otherwise specified | Mar. 31, 2015 | Dec. 31, 2014
--- | --- | ---
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 3,649,632 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial | $ 2,892,522 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial
Total percentage of recorded investment in commercial loan | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage
Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 3,458,560 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 2,780,315 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Total percentage of recorded investment in commercial loan | 94.80%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 96.10%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 101,333 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 65,968 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Total percentage of recorded investment in commercial loan | 2.80%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 2.30%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 89,739 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 46,239 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Total percentage of recorded investment in commercial loan | 2.40%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 1.60%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Commercial Real Estate [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 2,152,413 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember | 1,682,236 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember
Total percentage of recorded investment in commercial loan | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember
Commercial Real Estate [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 2,073,492 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 1,635,132 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Total percentage of recorded investment in commercial loan | 96.30%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 97.20%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Commercial Real Estate [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 25,204 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 23,597 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Total percentage of recorded investment in commercial loan | 1.20%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 1.40%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Commercial Real Estate [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 53,717 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 23,507 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Total percentage of recorded investment in commercial loan | 2.50%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 1.40%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Commercial and Industrial [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 1,211,053 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember | 994,138 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember
Total percentage of recorded investment in commercial loan | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember
Commercial and Industrial [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 1,137,101 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 948,663 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Total percentage of recorded investment in commercial loan | 93.90%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 95.40%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Commercial and Industrial [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 55,529 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 30,357 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Total percentage of recorded investment in commercial loan | 4.60%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 3.10%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Commercial and Industrial [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 18,423 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 15,118 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Total percentage of recorded investment in commercial loan | 1.50%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 1.50%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Commercial Construction [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 286,166 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember | 216,148 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember
Total percentage of recorded investment in commercial loan | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember | 100.00%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember
Commercial Construction [Member] | Pass [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 247,967 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 196,520 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Total percentage of recorded investment in commercial loan | 86.70%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember | 90.90%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_PassMember
Commercial Construction [Member] | Special Mention [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | 20,600 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 12,014 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Total percentage of recorded investment in commercial loan | 7.20%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember | 5.60%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SpecialMentionMember
Commercial Construction [Member] | Substandard [Member] |  |
Financing Receivable, Recorded Investment [Line Items] |  |
Total recorded investment in commercial loan | $ 17,599 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | $ 7,614 us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember
Total percentage of recorded investment in commercial loan | 6.10%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember | 3.50%stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember / us-gaap_InternalCreditAssessmentAxis = us-gaap_SubstandardMember

X
- Definition Loans and leases receivable gross carrying amount commercial percentage. + References No definition available. + Details
Name: | stba_LoansAndLeasesReceivableGrossCarryingAmountCommercialPercentage
Namespace Prefix: | stba_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Reflects the aggregate gross carrying amount of all commercial loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on commercial loans and leases. + References Reference 1: 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=35738203&loc=d3e5074-111524 Reference 2: 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=28367877&loc=d3e4428-111522 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5066-111524 + Details
Name: | us-gaap_LoansAndLeasesReceivableGrossCarryingAmountCommercial
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

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

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