XML 81 R41.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Securities - Unrealized Gains (Losses) of Debt Securities (Details) - USD ($) $ in Thousands | Mar. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Investments, Debt and Equity Securities [Abstract] |  |
Total unrealized gains (losses) on debt securities available-for-sale, Gross Unrealized Losses | $ 3,070 | $ 5,645
Total unrealized gains (losses) on debt securities available-for-sale, Gross Unrealized Losses | (10,867) | (3,967)
Total unrealized gains (losses) on debt securities available-for-sale, Net Unrealized Gains/(Losses) | (7,797) | 1,678
Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Gain Adjustment, Tax Expense (Benefit) | (652) | (1,982)
Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Loss Adjustment, Tax Expense (Benefit) | 2,308 | 1,393
Accumulated Other Comprehensive Income (Loss), Debt Securities Available-for-sale Adjustment, Tax Expense (Benefit) | 1,656 | (589)
Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Gain Adjustment Net Of Tax | 2,418 | 3,663
Accumulated Other Comprehensive Income (Loss), Debt Securities Available For Sale Gross Unrealized Losses Adjustment Net Of Tax | (8,559) | (2,574)
Accumulated Other Comprehensive Income (Loss), Debt Securities Available-for-sale Securities Adjustment, Net of Tax | $ (6,141) | $ 1,089

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 Accumulated Other Comprehensive Income (Loss), Debt Securities Available-for-sale Securities Adjustment, Net of Tax + References No definition available. + Details
Name: | stba_AccumulatedOtherComprehensiveIncomeLossDebtSecuritiesAvailableforsaleSecuritiesAdjustmentNetofTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Accumulated Gross Unrealized Gain, before Tax + References No definition available. + Details
Name: | stba_DebtSecuritiesAvailableforsaleAccumulatedGrossUnrealizedGainbeforeTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale, Accumulated Gross Unrealized Loss, before Tax + References No definition available. + Details
Name: | stba_DebtSecuritiesAvailableforsaleAccumulatedGrossUnrealizedLossbeforeTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Debt Securities, Available-for-sale Securities, Accumulated Gross Unrealized Gain (Loss), before Tax + References No definition available. + Details
Name: | stba_DebtSecuritiesAvailableforsaleSecuritiesAccumulatedGrossUnrealizedGainLossbeforeTax
Namespace Prefix: | stba_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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