Credit agreements, long-term debt and changes in long-term debt - Schedule of Line of Credit Facilities (Details) - Revolving Credit Facility - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Line of Credit Facility [Line Items]
Capacity	$ 844	$ 664
Outstanding	31	389
Undrawn	813	275
Hawaiian Electric Company, Inc. and Subsidiaries
Line of Credit Facility [Line Items]
Capacity	619	564
Outstanding	0	216
Undrawn	619	348
Unsecured revolving line of credit
Line of Credit Facility [Line Items]
Capacity	300	175
Outstanding	31	173
Undrawn	269	2
Unsecured revolving line of credit \| Hawaiian Electric Company, Inc. and Subsidiaries
Line of Credit Facility [Line Items]
Capacity	300	200
Outstanding	0	166
Undrawn	300	34
ABL Facility \| Hawaiian Electric Company, Inc. and Subsidiaries
Line of Credit Facility [Line Items]
Capacity	244	239
Outstanding	0	0
Undrawn	244	239
Borrowing from HEI - standing commitment letter \| Hawaiian Electric Company, Inc. and Subsidiaries
Line of Credit Facility [Line Items]
Capacity	75	75
Outstanding	0	0
Undrawn	75	75
Short-term loan credit facility \| Hawaiian Electric Company, Inc. and Subsidiaries
Line of Credit Facility [Line Items]
Capacity	0	50
Outstanding	0	50
Undrawn	$ 0	$ 0

Fair value of the amount outstanding under the credit facility.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

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- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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Balance Type:	credit
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- 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/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
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-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
-Name Accounting Standards Codification
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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