Bank segment (HEI only) - Loan Modifications (Details)	12 Months Ended
Dec. 31, 2017 USD ($) contract	Dec. 31, 2016 USD ($) contract	Dec. 31, 2015 USD ($) contract
Loan modifications determined to be troubled debt restructurings
Commitments to Borrowers whose Loan Terms are Impaired or Modified under Troubled Debt Restructuring	$ 0	$ 2,600,000
Troubled debt restructurings real estate loans
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	64	67	68
Pre-modification outstanding recorded investment	$ 4,798,000	$ 26,937,000	$ 10,020,000
Post-modification outstanding recorded investment	4,792,000	27,052,000	10,094,000
Net increase in ALLL	$ 877,000	$ 1,756,000	$ 943,000
Minimum period of payment default of loans determined to be TDRs	90 days	90 days	90 days
Troubled debt restructurings real estate loans \| Residential 1-4 family
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	7	14	19
Pre-modification outstanding recorded investment	$ 742,000	$ 3,131,000	$ 3,594,000
Post-modification outstanding recorded investment	750,000	3,245,000	3,668,000
Net increase in ALLL	$ 45,000	$ 337,000	$ 87,000
Troubled debt restructurings real estate loans \| Commercial real estate
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	1
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 1,500,000
Post-modification outstanding recorded investment	0	0	1,500,000
Net increase in ALLL	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Home equity line of credit
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	46	36	39
Pre-modification outstanding recorded investment	$ 3,016,000	$ 3,337,000	$ 2,441,000
Post-modification outstanding recorded investment	3,002,000	3,337,000	2,441,000
Net increase in ALLL	$ 557,000	$ 554,000	$ 370,000
Troubled debt restructurings real estate loans \| Residential land
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	1	2	1
Pre-modification outstanding recorded investment	$ 92,000	$ 203,000	$ 218,000
Post-modification outstanding recorded investment	92,000	204,000	218,000
Net increase in ALLL	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Commercial construction
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0
Net increase in ALLL	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Residential construction
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Pre-modification outstanding recorded investment	$ 0	$ 0	$ 0
Post-modification outstanding recorded investment	0	0	0
Net increase in ALLL	$ 0	$ 0	$ 0
Troubled debt restructurings real estate loans \| Commercial
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	9	15	8
Pre-modification outstanding recorded investment	$ 889,000	$ 20,266,000	$ 2,267,000
Post-modification outstanding recorded investment	889,000	20,266,000	2,267,000
Net increase in ALLL	$ 248,000	$ 865,000	$ 486,000
Troubled debt restructurings real estate loans \| Consumer
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	1	0	0
Pre-modification outstanding recorded investment	$ 59,000	$ 0	$ 0
Post-modification outstanding recorded investment	59,000	0	0
Net increase in ALLL	$ 27,000	$ 0	$ 0
Troubled debt restructurings that subsequently defaulted
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	1	2	2
Recorded investment	$ 222,000	$ 263,000	$ 1,062,000
Consumer mortgage loans collateralized by residential real estate property in foreclosure process	$ 4,300,000	$ 3,900,000
Troubled debt restructurings that subsequently defaulted \| Residential 1-4 family
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	1	1	0
Recorded investment	$ 222,000	$ 239,000	$ 0
Troubled debt restructurings that subsequently defaulted \| Commercial real estate
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Recorded investment	$ 0	$ 0	$ 0
Troubled debt restructurings that subsequently defaulted \| Home equity line of credit
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	1
Recorded investment	$ 0	$ 0	$ 6,000
Troubled debt restructurings that subsequently defaulted \| Residential land
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Recorded investment	$ 0	$ 0	$ 0
Troubled debt restructurings that subsequently defaulted \| Commercial construction
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Recorded investment	$ 0	$ 0	$ 0
Troubled debt restructurings that subsequently defaulted \| Residential construction
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Recorded investment	$ 0	$ 0	$ 0
Troubled debt restructurings that subsequently defaulted \| Commercial
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	1	1
Recorded investment	$ 0	$ 24,000	$ 1,056,000
Troubled debt restructurings that subsequently defaulted \| Consumer
Loan modifications determined to be troubled debt restructurings
Number of contracts \| contract	0	0	0
Recorded investment	$ 0	$ 0	$ 0

Represents the commitments to borrowers whose loan terms are impaired or modified under troubled debt restructuring.

No definition available.

Name:	he_CommitmentsToBorrowersWhoseLoanTermsAreImpairedOrModifiedUnderTroubledDebtRestructuring
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Financial Receivables, Loans Collateralized by Real Estate in Foreclosure

+ References

No definition available.

+ Details

Name:	he_FinancialReceivablesLoansCollateralizedbyRealEstateinForeclosure
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the minimum period of payment default of loans determined to be troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	he_FinancingReceivableModificationsMinimumPeriodOfPaymentDefaultOfLoansDeterminedToBeTroubledDebtRestructurings
Namespace Prefix:	he_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of contracts under financing receivables that have been modified by troubled debt restructurings during the period.

+ References

No definition available.

+ Details

Name:	he_FinancingReceivablesModificationsNumberOfContracts
Namespace Prefix:	he_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the outstanding recorded investment in financial receivables after the financial receivables being modified as troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	he_FinancingReceivablesModificationsPostModificationRecordedInvestment
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of the outstanding recorded investment in financial receivables prior to the financial receivables being modified as troubled debt restructurings.

+ References

No definition available.

+ Details

Name:	he_FinancingReceivablesModificationsPreModificationRecordedInvestment
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) of allowance reserve for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_AllowanceForLoanAndLeaseLossesPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
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_FinancingReceivableModificationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the outstanding recorded investment related to financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 40
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=25495931&loc=d3e18845-111554

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Recorded Investment
-URI http://asc.fasb.org/extlink&oid=65880944

+ Details

Name:	us-gaap_FinancingReceivableModificationsRecordedInvestment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	he_FinancingReceivableTroubledDebtRestructuringsAndTroubledDebtRestructuringsThatSubsequentlyDefaultedAxis=he_FinancingReceivableTroubledDebtRestructuringsRealEstateLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=he_Residential1To4FamilyPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_HomeEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=he_ResidentialLandPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConstructionLoansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=he_ResidentialConstructionPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	he_FinancingReceivableTroubledDebtRestructuringsAndTroubledDebtRestructuringsThatSubsequentlyDefaultedAxis=he_FinancingReceivableTroubledDebtRestructuringsThatSubsequentlyDefaultedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: