XML 97 R81.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Allowance for Loan Losses - Summary of Allowance for Loan Losses (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | $ 52,775 |  |  |  | $ 48,147 | $ 52,775 | $ 48,147 |
Charge-offs |  |  |  |  |  |  |  |  | (13,496) | (15,561) |
Recoveries |  |  |  |  |  |  |  |  | 3,228 | 2,224 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (10,268) | (13,337) |
Provision for loan losses | $ 982 | $ 2,850 | $ 4,869 | 5,183 | $ 5,586 | $ 2,516 | $ 4,848 | 5,014 | 13,883 | 17,965 | $ 10,388
Balance at End of Year | 56,390 |  |  |  | 52,775 |  |  |  | 56,390 | 52,775 | 48,147
Commercial real estate |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | 19,976 |  |  |  | 15,043 | 19,976 | 15,043 |
Charge-offs |  |  |  |  |  |  |  |  | (2,304) | (3,114) |
Recoveries |  |  |  |  |  |  |  |  | 810 | 692 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (1,494) | (2,422) |
Provision for loan losses |  |  |  |  |  |  |  |  | 8,753 | 7,355 |
Balance at End of Year | 27,235 |  |  |  | 19,976 |  |  |  | 27,235 | 19,976 | 15,043
Commercial and industrial |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | 10,810 |  |  |  | 10,853 | 10,810 | 10,853 |
Charge-offs |  |  |  |  |  |  |  |  | (4,709) | (6,810) |
Recoveries |  |  |  |  |  |  |  |  | 654 | 722 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (4,055) | (6,088) |
Provision for loan losses |  |  |  |  |  |  |  |  | 2,211 | 6,045 |
Balance at End of Year | 8,966 |  |  |  | 10,810 |  |  |  | 8,966 | 10,810 | 10,853
Commercial construction |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | 13,999 |  |  |  | 12,625 | 13,999 | 12,625 |
Charge-offs |  |  |  |  |  |  |  |  | (2,571) | (1,877) |
Recoveries |  |  |  |  |  |  |  |  | 851 | 21 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (1,720) | (1,856) |
Provision for loan losses |  |  |  |  |  |  |  |  | 888 | 3,230 |
Balance at End of Year | 13,167 |  |  |  | 13,999 |  |  |  | 13,167 | 13,999 | 12,625
Consumer real estate |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | 6,095 |  |  |  | 8,400 | 6,095 | 8,400 |
Charge-offs |  |  |  |  |  |  |  |  | (2,274) | (1,657) |
Recoveries |  |  |  |  |  |  |  |  | 342 | 433 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (1,932) | (1,224) |
Provision for loan losses |  |  |  |  |  |  |  |  | 1,316 | (1,081) |
Balance at End of Year | 5,479 |  |  |  | 6,095 |  |  |  | 5,479 | 6,095 | 8,400
Other consumer |  |  |  |  |  |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Roll Forward] |  |  |  |  |  |  |  |  |  |  |
Balance at beginning of year |  |  |  | $ 1,895 |  |  |  | $ 1,226 | 1,895 | 1,226 |
Charge-offs |  |  |  |  |  |  |  |  | (1,638) | (2,103) |
Recoveries |  |  |  |  |  |  |  |  | 571 | 356 |
Net (Charge-offs) Recoveries |  |  |  |  |  |  |  |  | (1,067) | (1,747) |
Provision for loan losses |  |  |  |  |  |  |  |  | 715 | 2,416 |
Balance at End of Year | $ 1,543 |  |  |  | $ 1,895 |  |  |  | $ 1,543 | $ 1,895 | $ 1,226

X
- Definition Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(4) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_AllowanceForLoanAndLeaseLossRecoveryOfBadDebts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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://www.xbrl.org/2003/role/presentationRef -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://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(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 Amount, after recoveries, of loans and leases that have been written-off. + References No definition available. + Details
Name: | us-gaap_AllowanceForLoanAndLeaseLossesWriteoffsNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance 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 10 -Section 50 -Paragraph 11B -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(1) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 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(d)) -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 310 -SubTopic 10 -Section S99 -Paragraph 4 -Subparagraph (SAB Topic 6.L.1) -URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 30 -Section 50 -Paragraph 2 -Subparagraph (b)(1)(ii) -URI http://asc.fasb.org/extlink&oid=82894903&loc=d3e15032-111544 + Details
Name: | us-gaap_LoansAndLeasesReceivableAllowance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expense related to estimated loss from loan and lease transactions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.11) -URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(2) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_ProvisionForLoanAndLeaseLosses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_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: |