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Significant group concentrations of credit risk (Details) | 12 Months Ended
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Dec. 31, 2021
Major customers |
Percentage of workforce covered by collective bargaining arrangement | 50.00%
Percentage of benchmark loan to appraisal ratio in excess of which mortgage insurance is required | 80.00%
American Savings Bank (ASB) |
Major customers |
Percentage of benchmark loan to appraisal ratio in excess of which mortgage insurance is required | 80.00%

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- Definition Represents the minimum benchmark percentage of loan to appraisal ratio which mortgage insurance is required as per the policy of the reporting entity. + References No definition available. + Details
Name: | he_MinimumBenchmarkPercentageOfLoanToAppraisalRatioWhichMortgageInsuranceIsRequired
Namespace Prefix: | he_
Data Type: | dtr-types:percentItemType
Balance Type: | na
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: | us-gaap_ConcentrationRiskLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Percentage of entity's employees covered by collective-bargaining arrangement (CBA) to all participants in multiemployer pension plan determined to be individually insignificant. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 80 -Section 50 -Paragraph 5 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947 + Details
Name: | us-gaap_MultiemployerPlanPensionInsignificantEmployeesCoveredByCollectiveBargainingArrangementToAllParticipantsPercentage
Namespace Prefix: | us-gaap_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | duration

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