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Proposed Merger (Details) (USD $) | 4 Months Ended | 0 Months Ended | 1 Months Ended |
--- | --- | --- | --- | ---
Mar. 31, 2015 complaint | Dec. 03, 2014 | Jan. 31, 2015 | Apr. 30, 2015 action
Business Acquisition [Line Items] |  |  |  |
Number of purported class action complaints filed | 8 us-gaap_LossContingencyNewClaimsFiledNumber |  |  |
NextEra Energy, Inc Merger |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Merger share conversion ratio |  | 0.2413 he_BusinessCombinationShareConversionRatio / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember |  |
Minimum percentage of shares from which holders approval needed for merger |  | 75.00%he_BusinessCombinationMinimumPercentageofSharesFromWhichHoldersApprovalNeededforMerger / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember |  |
Merger agreement contract extension |  | 6 months |  |
Merger contract termination fee |  | $ 90,000,000 he_BusinessCombinationMergerContractTerminationFee / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember |  |
Maximum expenses paid to party for cancellation of merger |  | 5,000,000 he_BusinessCombinationMaximumExpensesPaidtoPartyForCancellationofMergerAgreement / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember |  |
Minimum period that entity agrees not to submit applications for general base rate increase |  |  | 4 years |
Approximate amount of cumulative savings for customers due to forgone recoveries |  |  | $ 60,000,000 he_BusinessAcquisitionMergerAgreementForgoneRateAdjustmentApproximateCumulativeSavings / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember |
Hawaiian Electric Company, Inc. and Subsidiaries | NextEra Energy, Inc Merger |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Special dividend |  | $ 0.50 he_BusinessCombinationSpecialDividendPayablePerShare / us-gaap_BusinessAcquisitionAxis = he_NextEraEnergyIncMergerMember / dei_LegalEntityAxis = he_HawaiianElectricCompanyAndSubsidiariesMember |  |
In re Consolidated HEI Shareholder Cases | Subsequent Event |  |  |  |
Business Acquisition [Line Items] |  |  |  |
Consolidated number of state actions |  |  |  | 7 us-gaap_LossContingencyPendingClaimsNumber / us-gaap_LitigationCaseAxis = he_InReConsolidatedHEIShareholderCasesMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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- Definition The total number of new claims filed pertaining to a loss contingency during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 + Details
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