Bank segment - Credit risk profile - nonaccrual loans (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Mar. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Credit risk profile based on nonaccrual loans
With a Related ACL		$ 36,327
Without a Related ACL		10,652
Total		46,979	$ 29,736
Total troubled debt restructuring loans not included above	$ 26,413	24,378
Real estate \| Residential 1-4 family
Credit risk profile based on nonaccrual loans
With a Related ACL		7,584
Without a Related ACL		3,395
Total		10,979	11,395
Total troubled debt restructuring loans not included above	9,869	8,667
Real estate \| Commercial real estate
Credit risk profile based on nonaccrual loans
With a Related ACL		16,241
Without a Related ACL		0
Total		16,241	195
Total troubled debt restructuring loans not included above	853	1,016
Real estate \| Home equity line of credit
Credit risk profile based on nonaccrual loans
With a Related ACL		6,249
Without a Related ACL		1,616
Total		7,865	6,638
Total troubled debt restructuring loans not included above	10,376	9,430
Real estate \| Residential land
Credit risk profile based on nonaccrual loans
With a Related ACL		0
Without a Related ACL		413
Total		413	448
Total troubled debt restructuring loans not included above	2,644	2,007
Real estate \| Commercial construction
Credit risk profile based on nonaccrual loans
With a Related ACL		0
Without a Related ACL		2,289
Total		2,289	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
Without a Related ACL		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		616
Without a Related ACL		2,939
Total		3,555	5,947
Total troubled debt restructuring loans not included above	2,614	3,203
Consumer
Credit risk profile based on nonaccrual loans
With a Related ACL		5,637
Without a Related ACL		0
Total		5,637	$ 5,113
Total troubled debt restructuring loans not included above	$ 57	$ 55

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=121611835&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=121599337&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=121611835&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=121599337&loc=SL82919258-210447

+ 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: