Electric utility segment - Regulatory Proceedings (Details) $ in Thousands			9 Months Ended	12 Months Ended
	Dec. 29, 2023 USD ($)	Dec. 23, 2020 USD ($)	Sep. 30, 2024 USD ($) MWh project	Dec. 31, 2023 USD ($)	Dec. 31, 2019 USD ($) agreement	Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($) agreement	Mar. 11, 2024 USD ($)	Jun. 30, 2023 USD ($)	Jun. 17, 2022 mechanism	Jun. 10, 2019 USD ($)	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
Performance incentive mechanism, accrued award									$ 10
Potential total annual maximum reward			2,000
Regulatory assets			$ 314,247	$ 294,804
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Number of performance incentive mechanisms | mechanism										2
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			$ 38,000
EPRM approved projects | project			4
EPRM approved projects, capital costs			$ 218,500
Number of projects | project			2
Estimated capital costs			$ 294,200
Prior year deferred cost recovery approved								$ 3,000
Decoupling order, service reliability performance, historical measurement period (in years)			10 years
Maximum penalty, percent of ROE			0.20%
Service reliability, pending adjusted maximum penalty amount			$ 6,400
Service reliability, estimated penalties				3,700
Dead band percentage above or below the target			3.00%
Call center performance, maximum penalty percentage			0.08%
Call center performance, pending adjusted maximum penalty			$ 1,400
Number of power purchase agreements (PPAs) (in agreements) | agreement					7
Number of incentive earned power purchase agreements | agreement							2
Incentives accrued				100	$ 1,700		$ 100
Interpolated RPS rate goal, year one and two (in dollars per MWh) | MWh			20
Interpolated RPS rate goal, year three (in dollars per MWh) | MWh			15
Interpolated RPS rate goal, after year three (in dollars per MWh) | MWh			10
Failure to meet RPS targets, penalty rate (in dollars per MWh) | MWh			20
Accrued estimated rewards				400
Public utilities, grid services procurement performance incentive mechanism, accrued estimated rewards				1,100
Potential total annual maximum reward			$ 3,000
Total annual maximum penalty			900
Interconnection approval PIM, accrued estimated rewards				3,000
Performance incentive mechanism, maximum reward			$ 2,000
Target performance historical measurement period (in years)			10 years
Percent of return on equity			0.03%
Pending adjusted amount			$ 1,000
Target performance period (in months)			10 months
Target deadband period (in months)			2 months
Accrued earned rewards, net of penalties				900
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			$ 27,500
Hawaiian Electric Company, Inc. and Subsidiaries | Suspension Of Disconnections
Regulatory Projects and Legal Obligations [Line Items]
Regulatory assets			2,300
Hawaiian Electric Company, Inc. and Subsidiaries | Natural Disasters and Other Casualty Events
Regulatory Projects and Legal Obligations [Line Items]
Regulatory assets			38,800
Hawaiian Electric Company, Inc. and Subsidiaries | COVID-19
Regulatory Projects and Legal Obligations [Line Items]
Public utilities in regulatory assets	$ 8,800
Regulatory assets			$ 7,500
Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
Public utilities retained percentage			20.00%
Accrued earned rewards, net of penalties				1,200
Hawaii Electric Light Company, Inc
Regulatory Projects and Legal Obligations [Line Items]
Incentives accrued						$ 100
Accrued earned rewards, net of penalties				(600)
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Accrued earned rewards, net of penalties				$ 300
Schofield Generation Station | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount			$ 16,100
West Loch PV Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount			3,200
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount			16,100
Waiawa UFLS Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
EPRM requested amount			$ 100
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			$ 12,800
ERP/EAM Implementation Project | Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions			1,500
ERP/EAM Implementation Project | Hawaii Electric Light Company, Inc
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions			4,500
ERP/EAM Implementation Project | Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Regulatory liability for O&M expense reductions			6,800
Waena Switchyard/Synchronous Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
EPRM requested amount			$ 2,500