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Electric utility segment Additional Information (Details) (USD $)
 12 Months Ended 0 Months Ended 3 Months Ended 0 Months Ended 1 Months Ended 3 Months Ended
Dec. 31, 2014
agreement
Dec. 31, 2013
Dec. 31, 2012
Dec. 30, 2014
May 31, 2013
Nov. 30, 2013
Jun. 30, 2013
Jun. 30, 2014
Jul. 11, 2013
MW
Nov. 30, 2013
Feb. 28, 2013
bid
May 31, 2012
MW
Feb. 28, 2012
Dec. 31, 2009
Mar. 31, 2012
Dec. 31, 2011
Feb. 16, 2012
generation_unit
Feb. 07, 2014
Jul. 31, 2014
Power purchase agreements                                      
Number of power purchase agreements (PPAs) 7he_NumberOfPowerPurchaseAgreements                                    
Hawaiian Electric Company, Inc (HECO)                                      
Power purchase agreements                                      
Number of power purchase agreements (PPAs) 7he_NumberOfPowerPurchaseAgreements
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		                                    
Purchased power 537,821,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		 $ 527,839,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		 $ 540,802,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		                                
Renewable projects                                      
Number of Generating Units Subject to New Regulation                                 14he_NumberofGeneratingUnitsSubjecttoNewRegulation
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		    
D&O                                      
Revenues 2,142,245,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		 2,124,174,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		 2,228,233,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember		                                
Hawaii Electric Light Company, Inc. (HELCO)                                      
Power purchase agreements                                      
Purchased power 123,226,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		 128,368,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		 145,386,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		                                
D&O                                      
Revenues 422,200,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		 431,517,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		 441,013,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember		                                
Maui Electric Company, Limited (MECO)                                      
Power purchase agreements                                      
Purchased power 60,961,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		 54,474,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		 38,052,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                
Environmental regulation                                      
Additional accrued investigation and estimated cleanup costs 3,600,000he_ReserveForAdditionalInvestigationAndEstimatedCleanupCosts
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                           3,100,000he_ReserveForAdditionalInvestigationAndEstimatedCleanupCosts
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		        
D&O                                      
Revenues 422,965,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		 424,603,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		 440,270,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		   5,300,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                            
Reductions in D&O                                      
Lower ROACE   4,000,000he_LowerReturnOnCommonEquity
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Customer Information System expenses   300,000he_CustomerInformationSystemExpenses
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Pension and OPEB expense based on 3-year average   1,500,000he_PensionAndOPEBExpense
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Integrated resource planning expenses   900,000he_IntegratedResourcePlanningExpenses
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Operational and Renewable Energy Integration study costs   1,100,000he_StudyCosts
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Total adjustment 7,800,000he_AdjustmentsForDecisionAndOrderOfPUC
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		 7,800,000he_AdjustmentsForDecisionAndOrderOfPUC
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                  
Stipulated return on common equity percentage 10.00%he_StipulatedReturnOnCommonEquityPercentage
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Return on common equity percentage approved by PUC 9.00%he_ReturnOnCommonEquityPercentageApprovedByPUC
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Return on common equity percentage approved by PUC allocated to lower interest rate 0.50%he_ReturnOnCommonEquityPercentageApprovedByPUCAllocatedToLowerInterestRate
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Return on common equity percentage approved by PUC allocated for OverCurtailment of renewable energy 0.50%he_ReturnOnCommonEquityPercentageApprovedByPUCAllocatedForOverCurtailmentOfRenewableEnergy
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Period as basis for calculation of average pension cost 3 years                                    
Charge recorded net of revenue taxes             7,600,000he_ChargeRecordedNetOfRevenueTaxes
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                        
Amount to be refunded to customers           9,700,000he_AmountToBeRefundedToCustomers
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                          
Increase (decrease) in employee benefit expenses             (1,800,000)he_IncreaseDecreaseInEmployeeBenefitExpenses
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                        
Deferred IRP cost allowed by PUC order, reclassified to deferred accounts             700,000he_DeferredIRPCostAllowedByPUCOrderReclassifiedToDeferredAccounts
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                        
General Rate Case Cycle Period       3 years                              
Estimated increase in revenue, if base rate increased 11,600,000he_EstimatedIncreaseDecreaseInRevenueDueToChangeInBaseRate
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Estimated increase in revenue, if base rate increased, percentage 2.80%he_EstimatedIncreaseDecreaseInRevenueDueToChangeInBaseRatePercentage
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Estimated cost of common equity, percentage 10.75%he_EstimatedCostOfCommonEquityPercentage
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember		                                    
Hawaiian Electric Company, Inc. and Subsidiaries                                      
Fuel contracts                                      
Estimated cost of minimum purchase within 2015 year 400,000,000he_LongTermPurchaseCommitmentAmountWithinOneYear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Estimated cost of minimum purchase in 2016 year 300,000,000he_LongTermPurchaseCommitmentAmountInSecondYear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Estimated cost of minimum purchase in 2017 year 6,400,000he_LongTermPurchaseCommitmentAmountInThirdYear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Cost of purchases 1,100,000,000he_CostOfPurchases
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 1,100,000,000he_CostOfPurchases
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 1,300,000,000he_CostOfPurchases
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                
Power purchase agreements                                      
Power purchase capacity excluding agreements with smaller IPPs (in megawatts) 575he_AggregateOfPowerPurchaseCapacityExcludingAgreementWithSmallerIndependentPowerProducers
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Purchased power 722,008,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 710,681,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 724,240,000us-gaap_UtilitiesOperatingExpensePurchasedPower
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                
Expected fixed capacity charges per year for 2015 through 2019, minimum 100,000,000he_UtilitiesMinimumExpectedFixedCapacityChargesPerYearOneThroughFiveYears
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Expected fixed capacity charges from 2019 through 2033 500,000,000he_UtilitiesExpectedFixedCapacityChargesafterFiveThroughTwentyYears
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Renewable projects                                      
Percentage of renewable portfolio standard to be achieved by 2030                           40.00%he_PercentageOfExpectedRenewablePortfolioStandard
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		          
Recovery of annual deferred costs contingent on approval                   405,000he_PublicUtilitiesRecoveryOfAnnualDeferredCostsContingentOnApproval
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                  
Integration from renewable energy sources (in megawatts)   200he_CapacityIntegrationFromRenewableEnergySources
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		             200he_CapacityIntegrationFromRenewableEnergySources
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                    
Maximum deferred cost recovery                         5,890,000he_UtilitiesMaximumDeferredCostRecoveryPerYear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		            
Integration from firm renewable geothermal dispatchable energy (in megawatts)                       50he_CapacityIntegrationFromDispatchableRenewableGeothermalSources
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		              
Number of bids received                     6he_NumberOfBidsReceived
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                
Environmental regulation                                      
Percentage of reduction in GHG emissions by 2020               16.00%he_PercentageOfGreenHouseGasEmissionBy2020
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                      
Estimated annual fee, emissions regulation 500,000he_EmissionsRegulationsEstimatedAnnualFee
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
D&O                                      
Revenues 2,987,323,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 2,980,172,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 3,109,439,000us-gaap_RegulatedOperatingRevenueElectricNonNuclear
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                
Changes in the asset retirement obligation liability                                      
Balance at the beginning of the period 43,106,000us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 48,431,000us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                  
Accretion expense 890,000us-gaap_AssetRetirementObligationAccretionExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 1,263,000us-gaap_AssetRetirementObligationAccretionExpense
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                  
Liabilities incurred 0us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 0us-gaap_AssetRetirementObligationLiabilitiesIncurred
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                  
Liabilities settled (14,577,000)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 (5,672,000)us-gaap_AssetRetirementObligationLiabilitiesSettled
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                  
Revisions in estimated cash flows 0us-gaap_AssetRetirementObligationRevisionOfEstimate
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 (916,000)us-gaap_AssetRetirementObligationRevisionOfEstimate
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                  
Balance at the end of the period 29,419,000us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 43,106,000us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		 48,431,000us-gaap_AssetRetirementObligation
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                
Decoupling                                      
Public Utilities, baseline capital project value to determine revenue adjustment 2,500,000he_PublicUtilitiesBaselineCapitalProjectValuetoDetermineRevenueAdjustment
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Public Utilities, proposed rate base adjustment, percent of previous rate base adjustment                                   90.00%he_PublicUtilitiesProposedRateBaseAdjustmentPercentofPreviousRateBaseAdjustment
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		  
Public Utilites, effective interest rate, revenue balancing account 6.00%he_PublicUtilitiesEffectiveInterestRateRevenueBalancingAccount
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember		                                    
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum                                      
Decoupling                                      
Public Utilities, proposed effective interest rate, revenue balancing account                                   1.25%he_PublicUtilitiesProposedEffectiveInterestRateRevenueBalancingAccount
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember		  
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum                                      
Decoupling                                      
Public Utilities, proposed effective interest rate, revenue balancing account                                   3.25%he_PublicUtilitiesProposedEffectiveInterestRateRevenueBalancingAccount
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember		  
East Oahu Transmission Project Phase 1 | Hawaiian Electric Company, Inc. and Subsidiaries                                      
Renewable projects                                      
Gross plant cost agreed to be written-off in lieu of regulatory audit                             9,500,000he_PlantCostAgreedToBeWrittenOff
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_EastOahuTransmissionProjectPhase1Member		        
After-tax charge to net income due to settlement agreement                               6,000,000he_ImpactOfSettlementAgreementOnNetIncomeLossNetOfTax
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_EastOahuTransmissionProjectPhase1Member		      
Additional increase in test year rate case                             5,000,000he_AdditionalIncreaseinTestYearRateCase
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_EastOahuTransmissionProjectPhase1Member		        
Reserve for environmental costs                                      
Environmental regulation                                      
Reserve for additional investigation                                     $ 800,000us-gaap_ValuationAllowancesAndReservesBalance
/ us-gaap_ValuationAllowancesAndReservesTypeAxis
= us-gaap_ReserveForEnvironmentalCostsMember