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BENEFIT PLANS: Defined Benefit Plan, Assumptions Used in Calculations, Benefit Obligations (Details)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Pension Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Discount Rate 4.25%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		 5.20%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		  
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 4.30%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		 [1] 4.38%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
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= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		  
Measurement Date 12/31/2014 12/31/2013  
Senior Management Security Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Discount Rate 4.20%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		 5.10%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
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= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		  
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 4.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
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= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		 4.50%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
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= us-gaap_SupplementalEmployeeRetirementPlanDefinedBenefitMember		  
Measurement Date 12/31/2014 12/31/2013  
Postretirement Benefits      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Discount Rate 4.20%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_DefinedBenefitPostretirementHealthCoverageMember		 5.15%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationDiscountRate
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember		  
Measurement Date 12/31/2014 12/31/2013  
Medical trend rate | Postretirement Benefits      
Defined Benefit Plan Disclosure      
Health Care Cost Trend Rate Assumed for Next Fiscal Year 6.40%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_MedicalTrendRateMember		 6.80%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
/ us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis
= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_MedicalTrendRateMember		 6.50%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_MedicalTrendRateMember
Dental trend rate | Postretirement Benefits      
Defined Benefit Plan Disclosure      
Health Care Cost Trend Rate Assumed for Next Fiscal Year 5.00%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_DentalTrendRateMember		 5.00%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_DentalTrendRateMember		 5.00%us-gaap_DefinedBenefitPlanHealthCareCostTrendRateAssumedForNextFiscalYear
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= us-gaap_DefinedBenefitPostretirementHealthCoverageMember
/ ida_HealthCareTrendRateTypeAxis
= ida_DentalTrendRateMember
Inflation rate | Pension Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 2.75%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ida_CompensationIncreaseAssumptionsAxis
= ida_InflationRateMember
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= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		    
Composite merit increase | Pension Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 1.55%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ida_CompensationIncreaseAssumptionsAxis
= ida_CompositeMeritIncreaseMember
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= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		    
Merit salary increase first year of service | Pension Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 8.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ida_CompensationIncreaseAssumptionsAxis
= ida_MeritSalaryIncreaseFirstYearOfServiceMember
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= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		    
Merit salary increase fortieth year of service and beyond | Pension Plan      
Defined Benefit Plan Disclosure      
Assumptions Used Calculating Benefit Obligation, Rate of Compensation Increase 0.00%us-gaap_DefinedBenefitPlanAssumptionsUsedCalculatingBenefitObligationRateOfCompensationIncrease
/ ida_CompensationIncreaseAssumptionsAxis
= ida_MeritSalaryIncreaseFortiethYearOfServiceAndBeyondMember
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= us-gaap_UnitedStatesPensionPlansOfUSEntityDefinedBenefitMember		    
[1] The 2014 rate of compensation increase assumption for the pension plan includes an inflation component of 2.75% plus a 1.55% composite merit increase component that is based on employees' years of service. Merit salary increases are assumed to be 8.0% for employees in their first year of service and scale down to 0% for employees in their fortieth year of service and beyond.