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Accumulated Other Comprehensive Loss (AOCL) (Reclassification out of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified | 12 Months Ended
--- | ---
Dec. 31, 2014 | Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Interest on investment securities: Taxable | $ 6,981 us-gaap_InterestIncomeSecuritiesTaxable | $ 5,557 us-gaap_InterestIncomeSecuritiesTaxable
Gain Loss Other | 1,053 func_GainLossOther | 229 func_GainLossOther
Salaries and employee benefits | (19,518)us-gaap_LaborAndRelatedExpense | (19,946)us-gaap_LaborAndRelatedExpense
Tax expense (benefit) | (1,271)us-gaap_IncomeTaxExpenseBenefit | (2,222)us-gaap_IncomeTaxExpenseBenefit
Net income | 5,597 us-gaap_NetIncomeLoss | 6,475 us-gaap_NetIncomeLoss
Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Net income | 9 us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember | 52 us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember
Parent Company [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Tax expense (benefit) | 3,120 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 1,002 us-gaap_IncomeTaxExpenseBenefit / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Net income | 5,597 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember | 6,475 us-gaap_NetIncomeLoss / dei_LegalEntityAxis = us-gaap_ParentCompanyMember
Investment securities- with OTTI AFS [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Interest on investment securities: Taxable | 674 us-gaap_InterestIncomeSecuritiesTaxable / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember | 537 us-gaap_InterestIncomeSecuritiesTaxable / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember
Tax expense (benefit) | (269)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember | (215)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember
Net income | 405 us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember | 322 us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedOtherThanTemporaryImpairmentMember
Investment securities- all other [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Gain Loss Other | (41)func_GainLossOther / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember | 78 func_GainLossOther / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Tax expense (benefit) | 16 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember | (31)us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Net income | (25)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember | 47 us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember
Investment Securities HTM [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Interest on investment securities: Taxable | (233)us-gaap_InterestIncomeSecuritiesTaxable / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedNetUnrealizedInvestmentGainLossHeldToMaturityMember |
Tax expense (benefit) | 93 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedNetUnrealizedInvestmentGainLossHeldToMaturityMember |
Net income | (140)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedNetUnrealizedInvestmentGainLossHeldToMaturityMember |
Pension Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Tax expense (benefit) | 138 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | 202 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Net income | (209)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | (303)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Pension Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Unrecognized Loss [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Salaries and employee benefits | (374)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfUnrecognizedLossMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | (532)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfUnrecognizedLossMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Pension Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Transition Asset [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Salaries and employee benefits | 39 us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfTransitionAssetMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | 39 us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfTransitionAssetMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
Pension Plan [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Prior Service Costs [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Salaries and employee benefits | (12)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfPriorServiceCostsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember | (12)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfPriorServiceCostsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember
SERP [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Tax expense (benefit) | 15 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember | 9 us-gaap_IncomeTaxExpenseBenefit / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember
Net income | (22)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember | (14)us-gaap_NetIncomeLoss / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember
SERP [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Unrecognized Loss [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Salaries and employee benefits | (17)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfUnrecognizedLossMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember | (3)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfUnrecognizedLossMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember
SERP [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of Prior Service Costs [Member] |  |
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items] |  |
Salaries and employee benefits | $ (20)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfPriorServiceCostsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember | $ (20)us-gaap_LaborAndRelatedExpense / us-gaap_OtherComprehensiveIncomeLocationAxis = func_AmortizationOfPriorServiceCostsMember / us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis = us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember / us-gaap_StatementEquityComponentsAxis = func_AccumulatedSupplementalEmployeeRetirementPlanAdjustmentMember

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