Bank segment - Credit risk profile - nonaccrual loans (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2021	Dec. 31, 2020
Credit risk profile based on nonaccrual loans
With a Related ACL	$ 39,950	$ 36,491
Without a Related ACL	13,323	10,905
Total	53,273	47,396
Total troubled debt restructuring loans not included above	24,722	27,078
Real estate \| Residential 1-4 family
Credit risk profile based on nonaccrual loans
With a Related ACL	14,076	8,991
Without a Related ACL	7,666	2,835
Total	21,742	11,826
Total troubled debt restructuring loans not included above	7,596	7,932
Real estate \| Commercial real estate
Credit risk profile based on nonaccrual loans
With a Related ACL	15,514	15,847
Without a Related ACL	1,437	2,875
Total	16,951	18,722
Total troubled debt restructuring loans not included above	3,203	3,281
Real estate \| Home equity line of credit
Credit risk profile based on nonaccrual loans
With a Related ACL	5,200	5,791
Without a Related ACL	1,415	1,567
Total	6,615	7,358
Total troubled debt restructuring loans not included above	7,617	8,148
Real estate \| Residential land
Credit risk profile based on nonaccrual loans
With a Related ACL	801	108
Without a Related ACL	300	300
Total	1,101	408
Total troubled debt restructuring loans not included above	995	1,555
Real estate \| Commercial construction
Credit risk profile based on nonaccrual loans
With a Related ACL	0	0
Without a Related ACL	0	0
Total	0	0
Total troubled debt restructuring loans not included above	0	0
Real estate \| Residential construction
Credit risk profile based on nonaccrual loans
With a Related ACL	0	0
Without a Related ACL	0	0
Total	0	0
Total troubled debt restructuring loans not included above	0	0
Commercial
Credit risk profile based on nonaccrual loans
With a Related ACL	1,718	1,819
Without a Related ACL	2,505	3,328
Total	4,223	5,147
Total troubled debt restructuring loans not included above	5,258	6,108
Consumer
Credit risk profile based on nonaccrual loans
With a Related ACL	2,641	3,935
Without a Related ACL	0	0
Total	2,641	3,935
Total troubled debt restructuring loans not included above	$ 53	$ 54

Financing Receivable, Nonaccrual, With Allowance

No definition available.

Name:	he_FinancingReceivableNonaccrualWithAllowance
Namespace Prefix:	he_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after troubled debt restructuring, of modified financing receivable.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=123577603&loc=SL6953676-111524

+ Details

Name:	us-gaap_FinancingReceivableModificationsPostModificationRecordedInvestment2
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of financing receivable on nonaccrual status with no allowance for credit loss.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

+ Details

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

- Definition

Amount of financing receivable on nonaccrual status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 7
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123577603&loc=d3e5111-111524

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 16
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124255953&loc=SL82919258-210447

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (3)

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1405
-Paragraph (a)
-Subparagraph (2)

+ Details

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

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=he_RealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=he_Residential14FamilyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivablePortfolioSegmentAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: