XML 63 R53.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Allowance for Loan Losses - Summary of Allowance for Loan Losses and Recorded Investments (Details) - USD ($) $ in Thousands | Sep. 30, 2017 | Jun. 30, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Dec. 31, 2015
--- | --- | --- | --- | --- | --- | ---
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | $ 312 |  | $ 798 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 56,400 |  | 51,977 |  |  |
Total Allowance for Loan Losses | 56,712 | $ 55,351 | 52,775 | $ 53,793 | $ 52,213 | $ 48,147
Portfolio Loans, Individually Evaluated for Impairment | 31,988 |  | 41,935 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 5,788,770 |  | 5,569,484 |  |  |
Total Portfolio Loans | 5,820,758 |  | 5,611,419 |  |  |
Commercial Real Estate |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | 0 |  | 0 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 24,975 |  | 19,976 |  |  |
Total Allowance for Loan Losses | 24,975 | 24,358 | 19,976 | 20,393 | 15,978 | 15,043
Portfolio Loans, Individually Evaluated for Impairment | 6,341 |  | 16,352 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 2,675,352 |  | 2,482,124 |  |  |
Total Portfolio Loans | 2,681,693 |  | 2,498,476 |  |  |
Commercial and Industrial |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | 260 |  | 771 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 9,454 |  | 10,039 |  |  |
Total Allowance for Loan Losses | 9,714 | 9,256 | 10,810 | 12,294 | 14,771 | 10,853
Portfolio Loans, Individually Evaluated for Impairment | 8,543 |  | 6,866 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 1,438,268 |  | 1,394,169 |  |  |
Total Portfolio Loans | 1,446,811 |  | 1,401,035 |  |  |
Commercial Construction |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | 0 |  | 0 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 14,915 |  | 13,999 |  |  |
Total Allowance for Loan Losses | 14,915 | 13,944 | 13,999 | 12,911 | 11,701 | 12,625
Portfolio Loans, Individually Evaluated for Impairment | 5,974 |  | 6,613 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 426,913 |  | 449,271 |  |  |
Total Portfolio Loans | 432,887 |  | 455,884 |  |  |
Consumer Real Estate |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | 22 |  | 26 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 5,509 |  | 6,069 |  |  |
Total Allowance for Loan Losses | 5,531 | 5,803 | 6,095 | 6,333 | 8,418 | 8,400
Portfolio Loans, Individually Evaluated for Impairment | 11,076 |  | 12,079 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 1,178,647 |  | 1,178,093 |  |  |
Total Portfolio Loans | 1,189,723 |  | 1,190,172 |  |  |
Other Consumer |  |  |  |  |  |
Financing Receivable, Allowance for Credit Losses [Line Items] |  |  |  |  |  |
Allowance for Loan Losses, Individually Evaluated for Impairment | 30 |  | 1 |  |  |
Allowance for Loan Losses, Collectively Evaluated for Impairment | 1,547 |  | 1,894 |  |  |
Total Allowance for Loan Losses | 1,577 | $ 1,990 | 1,895 | $ 1,862 | $ 1,345 | $ 1,226
Portfolio Loans, Individually Evaluated for Impairment | 54 |  | 25 |  |  |
Portfolio Loans, Collectively Evaluated for Impairment | 69,590 |  | 65,827 |  |  |
Total Portfolio Loans | $ 69,644 |  | $ 65,852 |  |  |

X
- Definition The valuation allowance for financing receivables that are expected to be uncollectible that were collectively evaluated for impairment. + 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 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of valuation allowance for financing receivables that are expected to be uncollectible that were individually evaluated for impairment. + 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 + Details
Name: | us-gaap_FinancingReceivableAllowanceForCreditLossesIndividuallyEvaluatedForImpairment1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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_FinancingReceivableAllowanceForCreditLossesLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The balance of financing receivables that were collectively evaluated for impairment. + 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 (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableCollectivelyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The balance of financing receivables that were individually evaluated for impairment. + 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 (h) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 + Details
Name: | us-gaap_FinancingReceivableIndividuallyEvaluatedForImpairment
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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 before allowance and after 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. 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 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 + Details
Name: | us-gaap_LoansAndLeasesReceivableNetOfDeferredIncome
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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: |