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Electric utility segment - Taxes (Details) - USD ($) $ in Millions | 3 Months Ended
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Mar. 31, 2018 | Mar. 31, 2017
Hawaiian Electric Company, Inc. and Subsidiaries |  |
Revenue taxes |  |
Revenue taxes included in operating revenues and in taxes other than income taxes expense | $ 51 | $ 46

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- Definition Represents the utility revenue taxes included in operating revenues and in taxes, other than income taxes expense. + References No definition available. + Details
Name: | he_ElectricUtilityRevenueTaxesIncludedInOperatingRevenuesAndInTaxesOtherThanIncomeTaxesExpense
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | he_RevenueTaxesLineItems
Namespace Prefix: | he_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | dei_LegalEntityAxis=he_HawaiianElectricCompanyAndSubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |