XML 91 R78.htm IDEA: XBRL DOCUMENT
v3.20.4

Securities - Unrealized Gains (Losses) (Details) - USD ($) $ in Thousands | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Total unrealized gains/(losses) on debt securities available-for-sale |  |
Gross Unrealized Gains | $ 33,478 | $ 11,659
Gross Unrealized Losses | (90) | (953)
Net Unrealized Gains (Losses) | 33,388 | 10,706
Income tax (expense) benefit, Gross Unrealized Gains | (7,128) | (2,486)
Income tax (expense) benefit, Gross Unrealized Losses | 19 | 203
Income tax (expense) benefit, Net Unrealized (Losses)/Gains | (7,109) | (2,283)
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss), Gross Unrealized Gains | 26,350 | 9,173
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss), Gross Unrealized Losses | (71) | (750)
Net unrealized gains/(losses), net of tax included in accumulated other comprehensive income/(loss), Net Unrealized Gains/(Losses) | $ 26,279 | $ 8,423

X
- Definition Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Gain Adjustment Net Of Tax + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleGrossUnrealizedGainAdjustmentNetOfTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Gain Adjustment, Tax Expense (Benefit) + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleGrossUnrealizedGainAdjustmentTaxExpenseBenefit
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Loss Adjustment, Tax Expense (Benefit) + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleGrossUnrealizedLossAdjustmentTaxExpenseBenefit
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Losses Adjustment Net Of Tax + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableForSaleGrossUnrealizedLossesAdjustmentNetOfTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Accumulated Other Comprehensive Income (Loss), Debt Securities Available-for-sale Adjustment, Tax Expense (Benefit) + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableforsaleAdjustmentTaxExpenseBenefit
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, after tax, of accumulated unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=121641772&loc=d3e681-108580 + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27161-111563 + Details
Name: | us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainLossBeforeTaxAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount, before tax, of unrealized gain (loss) in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale). + References No definition available. + Details
Name: | us-gaap_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainLossBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant