XML 57 R36.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Business Combinations - Additional Information (Details) (USD $) | 3 Months Ended | 0 Months Ended |
--- | --- | --- | ---
Mar. 31, 2015 | Mar. 31, 2014 | Mar. 04, 2015 | Dec. 31, 2014
Business Acquisition [Line Items] |  |  |  |
Goodwill | $ 290,617,000 us-gaap_Goodwill |  |  | $ 175,820,000 us-gaap_Goodwill
Carryover of allowance for loan losses | 0 stba_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAllowanceforLoanLosses |  |  |
Merger related expenses | 2,301,000 us-gaap_BusinessCombinationAcquisitionRelatedCosts | 0 us-gaap_BusinessCombinationAcquisitionRelatedCosts |  |
Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Business acquisition, percentage of voting interests acquired |  |  | 100.00%us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Business acquisition, cash per share offered in exchange of share |  |  | $ 52.50 stba_BusinessAcquisitionShareholdersEntitledToReceiveCashForEachShare / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Shares of S&T offered for each share of Integrity (shares) |  |  | 2.0627 stba_BusinessAcquisitionNumberOfShareOfferedForEachShareOfAcquireeEntity / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Fair value of total consideration |  |  | 171,979,000 us-gaap_BusinessCombinationConsiderationTransferred1 / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Cash |  |  | 29,510,000 us-gaap_PaymentsToAcquireBusinessesGross / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
S&T common shares issued (shares) |  |  | 4,933,115 us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
S&T common shares issued, fair value (in USD per share) |  |  | $ 28.88 stba_BusinessCombinationConsiderationTransferredEquityInterestsIssuedandIssuableFairValuePerShare / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Goodwill |  |  | 114,797,000 us-gaap_Goodwill / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Carryover of allowance for loan losses |  |  | 0 stba_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAllowanceforLoanLosses / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Fair value of loans acquired |  |  | 788,687,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Discount on loans acquired |  |  | 14,800,000 stba_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoanDiscount / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |
Merger related expenses | 2,300,000 us-gaap_BusinessCombinationAcquisitionRelatedCosts / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |  |  |
Data processing, contract termination and conversion cost expenses | 900,000 stba_DataProcessingContractTerminationAndConversionCostExpenses / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |  |  |
Severance payments | 300,000 us-gaap_SeveranceCosts1 / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |  |  |
Legal And professional expenses | 1,100,000 stba_LegalAndProfessionalExpenses / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member |  |  |
Commercial Real Estate [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 481,400,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_CommercialRealEstateMember |
Commercial and Industrial [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 193,900,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialAndIndustrialMember |
Commercial Construction [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 44,800,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_CommercialConstructionMember |
Residential Mortgage [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 32,700,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_ResidentialMortgageMember |
Home Equity [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 28,800,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = us-gaap_HomeEquityMember |
Installment and Other Consumer [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | 5,600,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_InstallmentAndOtherConsumerMember |
Consumer Construction [Member] | Integrity Bancshares, Inc. [Member] |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Fair value of loans acquired |  |  | $ 1,500,000 us-gaap_BusinessCombinationAcquiredReceivablesFairValue / us-gaap_BusinessAcquisitionAxis = stba_IntegrityBancsharesInc.Member / us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis = stba_ConsumerConstructionMember |

X
- Definition Business acquisition number of share offered for each share of acquiree entity. + References No definition available. + Details
Name: | stba_BusinessAcquisitionNumberOfShareOfferedForEachShareOfAcquireeEntity
Namespace Prefix: | stba_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business acquisition shareholders entitled to receive cash for each share. + References No definition available. + Details
Name: | stba_BusinessAcquisitionShareholdersEntitledToReceiveCashForEachShare
Namespace Prefix: | stba_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Consideration Transferred, Equity Interests Issued and Issuable Fair Value, Per Share + References No definition available. + Details
Name: | stba_BusinessCombinationConsiderationTransferredEquityInterestsIssuedandIssuableFairValuePerShare
Namespace Prefix: | stba_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | duration

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Allowance for Loan Losses + References No definition available. + Details
Name: | stba_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedAllowanceforLoanLosses
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loan Discount + References No definition available. + Details
Name: | stba_BusinessCombinationRecognizedIdentifiableAssetsAcquiredandLiabilitiesAssumedLoanDiscount
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Data processing contract termination and conversion cost expenses. + References No definition available. + Details
Name: | stba_DataProcessingContractTerminationAndConversionCostExpenses
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Legal and professional expenses. + References No definition available. + Details
Name: | stba_LegalAndProfessionalExpenses
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of shares of equity interests issued or issuable to acquire entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b)(4) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

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

X
- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463 + Details
Name: | us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the fair value of the receivables acquired, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=39739317&loc=d3e4845-128472 + Details
Name: | us-gaap_BusinessCombinationAcquiredReceivablesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460 + Details
Name: | us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6578-128477 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=6911251&loc=d3e6613-128477 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 + Details
Name: | us-gaap_BusinessCombinationConsiderationTransferred1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266 + Details
Name: | us-gaap_Goodwill
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expenses for special or contractual termination benefits provided to current employees involuntarily terminated under a benefit arrangement associated exit or disposal activities pursuant to an authorized plan. Excludes expenses related to one-time termination benefits, a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.P.3) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a)(10) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
Name: | us-gaap_SeveranceCosts1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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_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=stba_ConsumerConstructionMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=stba_InstallmentAndOtherConsumerMember
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=us-gaap_HomeEquityMember
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: |