Represent the amount of maximum obligation to contribute additional capital under the Capital Maintenance Agreement.

No definition available.

Name:	he_ObligationToContributeAdditionalCapitalUnderCapitalMaintenanceAgreement
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the rate used to determine the prepaid risk-based assessments for financial institutions in the highest risk category.

+ References

No definition available.

+ Details

Name:	he_PrepaidAssessmentRateForFinancialInstitutionsInHighestRiskCategory
Namespace Prefix:	he_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represents the rate used to determine the prepaid risk-based assessments for financial institutions in the lowest risk category.

+ References

No definition available.

+ Details

Name:	he_PrepaidAssessmentRateForFinancialInstitutionsInLowestRiskCategory
Namespace Prefix:	he_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Represent the remaining amount of maximum obligation to contribute additional capital under the Capital Maintenance Agreement.

+ References

No definition available.

+ Details

Name:	he_RemainingObligationToContributeAdditionalCapitalUnderCapitalMaintenanceAgreement
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

This element represents disclosure of the total aggregate cash dividends paid to the entity by consolidated subsidiaries, by unconsolidated subsidiaries, and by 50% or less owned persons accounted for using the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(b))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24072-122690

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 235
-Section S99
-Paragraph 2
-Subparagraph (SX 210.9-06)
-URI http://asc.fasb.org/extlink&oid=6882215&loc=d3e537971-122884

+ Details

Name:	us-gaap_CashDividendsPaidToParentCompany
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Related Parties
-URI http://asc.fasb.org/extlink&oid=16382449

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07.1(c))
-URI http://asc.fasb.org/extlink&oid=6488393&loc=d3e606610-122999

+ Details

Name:	us-gaap_RevenueFromRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	dei_LegalEntityAxis=us-gaap_ParentCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=he_ConsolidatedSubsidiaryMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CounterpartyNameAxis=he_AmericanSavingsBankFSBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RelatedPartyTransactionAxis=he_ManagementandAdministrativeServicesMember
Namespace Prefix:
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Balance Type:
Period Type:

Bank segment (HEI only) - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 1988
Maximum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Prepaid assessment rate for financial institutions, lowest risk category	0.09%
Prepaid assessment rate for financial institutions, highest risk category	0.45%
Minimum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Prepaid assessment rate for financial institutions, lowest risk category	0.025%
Prepaid assessment rate for financial institutions, highest risk category	0.30%
American Savings Bank (ASB)
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Borrowing capacity	$ 1,800.0	$ 1,800.0
Cash dividends paid	37.5	36.0
Hawaiian Electric Industries, Inc.
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid	125.0	130.0	$ 121.0
Hawaiian Electric Industries, Inc. \| Consolidated subsidiary \| American Savings Bank (ASB) \| Management and administrative services
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Revenue from related party	2.1	$ 2.3	$ 2.1
Hawaiian Electric Industries, Inc. \| Maximum
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Obligation to contribute additional capital under the Capital Maintenance Agreement				$ 65.1
Reduction in obligation to contribute additional capital under the Capital Maintenance Agreement	$ 28.3