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Electric utility segment - Regulatory Proceedings (Details) $ in Thousands				9 Months Ended	12 Months Ended
	Oct. 06, 2025	Dec. 29, 2023 USD ($)	Dec. 23, 2020 USD ($)	Sep. 30, 2025 USD ($) project	Dec. 31, 2024 USD ($)	Mar. 24, 2025 USD ($)	Sep. 30, 2024	Dec. 22, 2023	Jun. 10, 2019 USD ($)	Oct. 31, 2018 USD ($)
Regulatory Projects and Legal Obligations [Line Items]
PUC proposal period (in days)			45 days
Public utilities, modified pilot process proposal period (in days)				15 days
Propose pilots annual cap				$ 10,000
Regulatory assets				$ 251,205	$ 227,424
Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
PUC planned period (in months)	17 months
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Multi-year rate period (in years)			5 years
Customer dividend, negative adjustment percentage			0.22%
Savings commitment liability, annual rate			$ 6,600
Earnings sharing mechanism, actual return on equity, dead band percentage above or below target				3.00%
Approved return on equity, percentage				9.50%
Percentage sharing between customers and utilities				0.50
Earnings sharing mechanism, actual earning, above or below dead band				1.50%
Percentage sharing for any further difference				0.90
MPIR and EPRM requested amount				$ 35,700
EPRM approved projects | project				4
EPRM approved projects, capital costs				$ 227,500
Number of projects | project				3
Prior year deferred cost recovery approved						$ 2,100
Performance incentive mechanism, (penalties) rewards				$ 300	6,200
Recovery of deferral costs period (in years)		3 years
Hawaiian Electric Company, Inc. and Subsidiaries | Honolulu Generating Units 8 and 9
Regulatory Projects and Legal Obligations [Line Items]
Regulatory asset amortization period								9 years
Regulatory assets				24,200
Hawaiian Electric Company, Inc. and Subsidiaries | Waiau Generating Units 3 and 4
Regulatory Projects and Legal Obligations [Line Items]
Regulatory asset amortization period							9 years
Regulatory assets				13,100
Hawaiian Electric Company, Inc. and Subsidiaries | Suspension Of Disconnections
Regulatory Projects and Legal Obligations [Line Items]
Regulatory assets				5,100
Hawaiian Electric Company, Inc. and Subsidiaries | Natural Disasters and Other Casualty Events
Regulatory Projects and Legal Obligations [Line Items]
Regulatory assets				74,500
Hawaiian Electric Company, Inc. and Subsidiaries | COVID-19
Regulatory Projects and Legal Obligations [Line Items]
Regulatory assets				4,400
Public utilities in regulatory assets		$ 8,700
Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
Performance incentive mechanism, (penalties) rewards					2,500
Hawaii Electric Light Company, Inc
Regulatory Projects and Legal Obligations [Line Items]
Performance incentive mechanism, (penalties) rewards					3,400
Phase 1 RFP, (penalties) rewards					200
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Performance incentive mechanism, (penalties) rewards					$ 300
Phase 1 RFP, (penalties) rewards				300
Schofield Generation Station | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount				15,600
West Loch PV Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount				3,100
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount				14,100
Waiawa UFLS Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
EPRM requested amount				100
Waena Switchyard/Synchronous Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
EPRM requested amount				2,500
Resilience Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
EPRM requested amount				$ 300
ERP/EAM Implementation Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
ERP/EAM project service period (in years)				12 years
ERP/EAM project service, savings over 12 years										$ 246,000
Future O&M expense reductions									$ 150,000
Future cost avoidance related to capital cost and tax costs									$ 96,000
Regulatory liability, amortization period (in years)				5 years
Regulatory liability for O&M expense reductions				$ 11,700
ERP/EAM Implementation Project | Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions				100
ERP/EAM Implementation Project | Hawaii Electric Light Company, Inc
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions				4,700
ERP/EAM Implementation Project | Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions				$ 6,900

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 980
-SubTopic 340
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478742/980-340-50-1

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