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interconnection (in kV)4false 5nve_UtilitiesAggregateShareTransmissionLineProjectnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.250.25falsefalsefalsenum:percentItemTypepureThe Utilities' aggregate share in the On Line project. a 250 mile 500 kV transmission lie connecting the northern and southern service territories.No definition available.false0Utilities' aggregate share in transmission line project (in hundredths)5false 5nve_RemainingShareTransmissionLineProjectnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truetruefalse0.750.75falsefalsefalsenum:percentItemTypepureGBT-South's share of the ON Line project, for which the Utilities have entered into a TUA with GBT-South in Phase I.No definition available.false0GBT-South's share in the ON Line project (in hundredths)6false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse2false 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6nve_LossContingencyAmountOfMinimumPunitiveDamagesSoughtnve_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse10000000001000000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryDescribes the amount of money award the plaintiff seeks for punitive damages in the legal matter.No definition available.false2Minimum punitive damages sought in DC Lawsuit10false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse3false USDtruefalse$AS_OF_Jun30_2013_dei_LegalEntityAxis_NevadaPowerCompanyMember_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_CapitalProjectsMemberhttp://www.sec.gov/CIK0000741508instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseNevada Power Company [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldinve_NevadaPowerCompanyMemberdei_LegalEntityAxisexplicitMemberfalsefalseCapital Projects [Member]us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxisxbrldihttp://xbrl.org/2006/xbrldinve_CapitalProjectsMemberus-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxisexplicitMemberUSDollarStandardhttp://www.xbrl.org/2003/iso4217USDiso42170USDUSD$nanafalse0Nevada Power Company [Member] | Capital Projects [Member]11true 4nve_TransmissionLineProjectAbstractnve_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0ON Line TUA [Abstract]12false 5nve_CapitalizedConstructionCostsAssociatedWithRemainingShareOfTransmissionLineProjectnve_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse336100000336100000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe amount of construction costs capitalized in CWIP associated with GBT's interest in the ON Line project, with a corresponding credit to other deferred liabilities.No definition available.false2Capitalized construction costs13false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse4false USDtruefalse$FROM_Jan01_2013_TO_Jun30_2013_dei_LegalEntityAxis_SierraPacificPowerCompanyMemberhttp://www.sec.gov/CIK0000741508duration2013-01-01T00:00:002013-06-30T00:00:00falsefalseSierra Pacific Power Company [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldinve_SierraPacificPowerCompanyMemberdei_LegalEntityAxisexplicitMemberUSDollarStandardhttp://www.xbrl.org/2003/iso4217USDiso42170MegaWattStandardhttp://www.xbrl.org/2009/utrMWutr0USDUSD$nanafalse0Sierra Pacific Power Company [Member]14true 5nve_HydroAbstractnve_falsenadurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00falsefalsefalsexbrli:stringItemTypestringfalse0Farad Dam [Abstract]15false 6nve_NumberOfHydroGeneratingUnitsSoldnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00fourfalsefalsefalsexbrli:stringItemTypestringNumber of hydro generating units, located in Nevada and California, sold to Truckee Meadows Water Authority.No definition available.false0Number of hydro generating units sold16false 6nve_TotalCapacityOfHydroGeneratingUnitsSoldnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse10.310.3falsefalsefalsexbrli:decimalItemTypedecimalTotal capacity, in MW, of hydro generating units, located in Nevada and California, sold to Truckee Meadows Water Authority.No definition available.false256Total capacity of hydro generating units sold (in MW)17false 6nve_ProceedsFromSaleOfHydroUnitsnve_falsedebitdurationfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse80000008000000USD$falsefalsefalsexbrli:monetaryItemTypemonetarySale of hydro units.No definition available.false2Proceeds from sale of hydro units18false 6nve_CapacityOfOutOfServiceGeneratingUnitnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2.82.8falsefalsefalsexbrli:decimalItemTypedecimalCapacity of the Farad Hydro generating unit, which has been out of service since the summer of 1996 due to a collapsed flume.No definition available.false256Capacity of the Farad Hydro generating unit (in MW)19false 6nve_EstimateToRebuildDiversionDamnve_falsecreditinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse2000000020000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryEstimate to rebuild the diversion dam of the Farad Hydro generating unit, which has been out of services since the summer of 1996 due to a collapsed flume.No definition available.false2Estimate to rebuild diversion dam of the Farad Hydro generating unit20false 6nve_AmountEntitledToRecoveredForCostsIncurredToDatenve_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1truefalsefalse40000004000000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryThe U.S. District Court for the District of Nevada ruling on the amount to be recovered for costs incurred to date.No definition available.false2Amount entitled to be recovered for costs incurred to date on Farad Dam21false 6nve_DurationPeriodToRebuildFaradDamnve_falsenainstantfalsefalsefalsefalsefalsefalsefalsefalseverboseLabel1falsefalsefalse00three yearsfalsefalsefalseus-types:durationStringItemTypenormalizedstringAmount of time from the date of the U.S. District Court for the District of Nevada's decision for the Farad dam to be rebuilt.No definition available.false0Duration to rebuild the Farad dam from the date of the Court's decision22false 6nve_Replacementcostnve_falsedebitinstantfalsefalsefalsefalsefalsefalsefalsefalse1truefalsefalse1980000019800000USD$falsefalsefalsexbrli:monetaryItemTypemonetaryValue of Farad Dam as set by the Ninth Circuit CourtNo definition available.false2ReplacementCost23false 0truefalsetruefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalse5false USDtruefalse$AS_OF_Jun30_2013_dei_LegalEntityAxis_SierraPacificPowerCompanyMember_us-gaap_UnrecordedUnconditionalPurchaseObligationByCategoryOfItemPurchasedAxis_CapitalProjectsMemberhttp://www.sec.gov/CIK0000741508instant2013-06-30T00:00:000001-01-01T00:00:00falsefalseSierra Pacific Power Company [Member]dei_LegalEntityAxisxbrldihttp://xbrl.org/2006/xbrldinve_SierraPacificPowerCompanyMemberdei_LegalEntityAxisexplicitMemberfalsefalseCapital Projects 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