XML 56 R41.htm IDEA: XBRL DOCUMENT
v3.5.0.2

Proposed Merger (Details) $ in Millions |  | 2 Months Ended | 3 Months Ended
--- | --- | --- | ---
Jul. 16, 2016 USD ($) | Jan. 21, 2015 complaint | Sep. 30, 2016 USD ($)
Business Acquisition [Line Items] |  |  |
Number of purported class action complaints filed | complaint |  | 8 |
NextEra Energy, Inc Merger | Scenario, Forecast |  |  |
Business Acquisition [Line Items] |  |  |
Recognition of previously disallowed merger expenses |  |  | $ 7.8
NextEra Energy, Inc Merger | Subsequent Event |  |  |
Business Acquisition [Line Items] |  |  |
Merger contract termination fee | $ 90.0 |  |
Maximum expenses paid to party for cancellation of merger | $ 5.0 |  |

X
- Definition Effective Income Tax Rate Reconciliation, Recognition Of Previously Disallowed Merger And Acquisition Expenses + References No definition available. + Details
Name: | he_EffectiveIncomeTaxRateReconciliationRecognitionOfPreviouslyDisallowedMergerAndAcquisitionExpenses
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Proceeds from Merger Related Cost Reimbursement + References No definition available. + Details
Name: | he_ProceedsfromMergerRelatedCostReimbursement
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Proceeds from Merger Termination Fee + References No definition available. + Details
Name: | he_ProceedsfromMergerTerminationFee
Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- 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_BusinessAcquisitionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- 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
Name: | us-gaap_LossContingencyNewClaimsFiledNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_BusinessAcquisitionAxis=he_NextEraEnergyIncMergerMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementScenarioAxis=us-gaap_ScenarioForecastMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |