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Electric utility segment - Unconsolidated variable interest entities (Details) - Hawaiian Electric Company | 9 Months Ended
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Sep. 30, 2018 agreement entity
Power purchase agreement |
Number of power purchase agreements (PPAs) (in agreements) | agreement | 5
Number of entities currently required to be consolidated as VIEs (in entities) | 0
Number of IPPs | 3
Number of firm capacity producers declining to provide financial information to determine primary beneficiary status (in entities) | 2
Minimum potential number of IPP entities consolidated into company in the future (in entities) | 1

X
- Definition The minimum number of potential IPP's that could be required to be consolidation into the Company in the future based on new financial information provided by IIP's used to determine VIE relationship. + References No definition available. + Details
Name: | he_MinimumPotentialNumberOfIPPEntitiesConsolidatedIntoCompanyInFuture
Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents information pertaining to number of firm capacity producers declining to provide financial information. + References No definition available. + Details
Name: | he_NumberOfFirmCapacityProducersDecliningToProvideFinancialInformation
Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number Of Independent Power Producers + References No definition available. + Details
Name: | he_NumberOfIndependentPowerProducers
Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of firm power purchase agreements entered into, by the company. + References No definition available. + Details
Name: | he_NumberOfPowerPurchaseAgreements
Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | he_PowerPurchaseAgreementAbstract
Namespace Prefix: | he_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the number of entities not required to be consolidated as VIEs. + References No definition available. + Details
Name: | he_VariableInterestEntityNumberOfUnconsolidatedVIEs
Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | srt_ConsolidatedEntitiesAxis=srt_SubsidiariesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |