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Electric utility segment 2014 Agreement (Details) (USD $)
In Millions, unless otherwise specified
 1 Months Ended 12 Months Ended
Apr. 30, 2014
order
Dec. 31, 2012
Jan. 28, 2013
Regulatory projects and legal obligations      
Remaining recoverable project costs included in rate base, in accordance with the settlement agreement   $ 52he_RemainingRecoverableProjectCostsIncludedInRateBaseAsPerSettlementAgreement  
Number of orders from regulatory agency 4he_PublicUtilitiesOrdersfromRegulatoryAgencyNumber    
Hawaiian Electric Company, Inc. and Subsidiaries      
Regulatory projects and legal obligations      
Period to file required plan 120 days    
Reliability standards, regulatory filing period 120 days    
Period to file implementation plan 60 days    
Period for full implementation of plan 180 days    
Period to file action plan 30 days    
Period to file implementation proposal 120 days    
Regulatory response filing period 90 days    
Hawaiian Electric Company, Inc. and Subsidiaries | CIS project      
Regulatory projects and legal obligations      
Project costs to be written off, subject to approval by PUC     40he_CostOfUtilitiesWriteOffOfProjectCostsSubjectToPUCApproval
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_CustomerInformationSystemProjectMember
After-tax charge to net income due to write-off of project costs   24.0he_ImpactOfWriteOffOfProjectCostsOnNetIncomeLossNetOfTax
/ dei_LegalEntityAxis
= he_HawaiianElectricCompanyAndSubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_CustomerInformationSystemProjectMember		  
HECO | CIS project      
Regulatory projects and legal obligations      
After-tax charge to net income due to write-off of project costs   17.1he_ImpactOfWriteOffOfProjectCostsOnNetIncomeLossNetOfTax
/ dei_LegalEntityAxis
= us-gaap_SubsidiariesMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_CustomerInformationSystemProjectMember		  
HELCO | CIS project      
Regulatory projects and legal obligations      
After-tax charge to net income due to write-off of project costs   3.4he_ImpactOfWriteOffOfProjectCostsOnNetIncomeLossNetOfTax
/ dei_LegalEntityAxis
= he_SubsidiariesTwoMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_CustomerInformationSystemProjectMember		  
MECO      
Regulatory projects and legal obligations      
Program and system information protocol, filing period 120 days    
MECO | CIS project      
Regulatory projects and legal obligations      
After-tax charge to net income due to write-off of project costs   $ 3.2he_ImpactOfWriteOffOfProjectCostsOnNetIncomeLossNetOfTax
/ dei_LegalEntityAxis
= he_SubsidiariesThreeMember
/ he_RegulatoryProjectsAndLegalObligationsAxis
= he_CustomerInformationSystemProjectMember