XML 103 R139.htm IDEA: XBRL DOCUMENT
v3.19.3.a.u2

Parent Company Condensed Financial Information - Statements of Net Income (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2019 | [1] | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2018 | Sep. 30, 2018 | Jun. 30, 2018 | Mar. 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Condensed Income Statements, Captions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total Interest Income | $ 82,457 | $ 79,813 | $ 79,624 | $ 78,590 | $ 76,589 | $ 73,627 | $ 71,581 | $ 68,029 | $ 320,484 | $ 289,826 | $ 260,642
Interest expense on long-term debt |  |  |  |  |  |  |  |  | 1,831 | 1,129 | 463
Income tax benefit | $ 5,091 | $ 4,743 | $ 5,070 | $ 4,222 | $ 4,952 | $ 2,876 | $ 4,010 | $ 6,007 | 19,126 | 17,845 | 46,437
Net Income |  |  |  |  |  |  |  |  | 98,234 | 105,334 | 72,968
Parent Company |  |  |  |  |  |  |  |  |  |  |
Condensed Income Statements, Captions [Line Items] |  |  |  |  |  |  |  |  |  |  |
Dividends from subsidiaries |  |  |  |  |  |  |  |  | 59,490 | 44,988 | 36,169
Investment income |  |  |  |  |  |  |  |  | 1 | 24 | 22
Total Interest Income |  |  |  |  |  |  |  |  | 59,491 | 45,012 | 36,191
Interest expense on long-term debt |  |  |  |  |  |  |  |  | 1,285 | 1,149 | 955
Other expenses |  |  |  |  |  |  |  |  | 4,325 | 3,988 | 3,801
Total Expense |  |  |  |  |  |  |  |  | 5,610 | 5,137 | 4,756
Income before income tax and undistributed net income of subsidiaries |  |  |  |  |  |  |  |  | 53,881 | 39,875 | 31,435
Income tax benefit |  |  |  |  |  |  |  |  | (1,189) | (1,093) | (1,596)
Income before undistributed net income of subsidiaries |  |  |  |  |  |  |  |  | 55,070 | 40,968 | 33,031
Equity in undistributed net income (distribution in excess of net income) of bank subsidiary |  |  |  |  |  |  |  |  | 42,683 | 68,385 | 40,877
Equity in undistributed net income (distribution in excess of net income) of nonbank subsidiaries |  |  |  |  |  |  |  |  | 481 | (4,019) | (940)
Net Income |  |  |  |  |  |  |  |  | $ 98,234 | $ 105,334 | $ 72,968
[1] | The DNB Merger is included in our consolidated financial statements beginning on December 1, 2019.

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: | srt_CondensedIncomeStatementsCaptionsLineItems
Namespace Prefix: | srt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Income before equity in undistributed earnings of subsidiaries. + References No definition available. + Details
Name: | stba_IncomeBeforeEquityInUndistributedEarningsOfSubsidiaries
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Income Before Taxes and Equity In Undistributed Earnings Of Subsidiaries + References No definition available. + Details
Name: | stba_IncomeBeforeTaxesandEquityInUndistributedEarningsOfSubsidiaries
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Income loss from equity method investments in bank subsidiaries. + References No definition available. + Details
Name: | stba_IncomeLossFromEquityMethodInvestmentsInBankSubsidiaries
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Income loss from equity method investments in non-bank subsidiaries. + References No definition available. + Details
Name: | stba_IncomeLossFromEquityMethodInvestmentsInNonbankSubsidiaries
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Interest And Other Expenses + References No definition available. + Details
Name: | stba_InterestAndOtherExpenses
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount before tax of income (loss) of subsidiary attributable to the parent entity. + References No definition available. + Details
Name: | us-gaap_IncomeLossFromSubsidiariesBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 280 -SubTopic 10 -Section 50 -Paragraph 22 -Subparagraph (h) -URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08(h)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 20 -Section 45 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=109238882&loc=d3e38679-109324 + Details
Name: | us-gaap_IncomeTaxExpenseBenefit
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the total of interest and dividend income, including any amortization and accretion (as applicable) of discounts and premiums, earned from (1) loans and leases whether held-for-sale or held-in-portfolio; (2) investment securities; (3) federal funds sold; (4) securities purchased under agreements to resell; (5) investments in banker's acceptances, commercial paper, or certificates of deposit; (6) dividend income; or (7) other investments not otherwise specified herein. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.1-5) -URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260 + Details
Name: | us-gaap_InterestAndDividendIncomeOperating
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Aggregate amount of interest paid or due on all long-term debt. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04.8) -URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260 + Details
Name: | us-gaap_InterestExpenseLongTermDebt
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount after accretion (amortization) of discount (premium), and investment expense, of interest income and dividend income on nonoperating securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.9) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(a),(b)) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 + Details
Name: | us-gaap_InvestmentIncomeNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The portion of profit or loss for the period, net of income taxes, which is attributable to the parent. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669619-108580 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-04(22)) -URI http://asc.fasb.org/extlink&oid=116637391&loc=SL114874048-224260 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 1B -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118930883&loc=SL7669625-108580 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04(18)) -URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263 Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03(20)) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 Reference 6: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585 Reference 7: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
Name: | us-gaap_NetIncomeLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of expense classified as other. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4,6) -URI http://asc.fasb.org/extlink&oid=116634182&loc=SL114868664-224227 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 220 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7) -URI http://asc.fasb.org/extlink&oid=116637232&loc=SL114874131-224263 + Details
Name: | us-gaap_OtherExpenses
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=srt_ParentCompanyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |