Electric utility segment - Utility Projects (Details) $ in Millions	6 Months Ended
	Jun. 30, 2023 USD ($)	Nov. 30, 2021 USD ($)	Oct. 31, 2020 generationUnit transmission_line kV	Jun. 10, 2019 USD ($)	Oct. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items]
Environmental loss contingency, statement of financial position, not disclosed	reserve account balance
Hawaiian Electric Company, Inc. and Subsidiaries | ERP/EAM Implementation Project
Public Utilities, General Disclosures [Line Items]
ERP/EAM project service period (in years)	12 years
ERP/EAM project service, savings over 12 years					$ 246.0
Future O&M expense reductions				$ 150.0
Future cost avoidance related to capital cost and tax costs				$ 96.0
Regulatory liability for O&M expense reductions	$ 11.5
Hawaiian Electric Company, Inc. and Subsidiaries | Waena Switchyard/Synchronous Condenser Project
Public Utilities, General Disclosures [Line Items]
Number of extended transmission lines | transmission_line			2
Number of kilovolts | kV			69
Number of generating units converting to synchronous condensers | generationUnit			2
Renewable energy generation project, approved funds		$ 38.8
Renewable energy generation project, incurred cost	21.2
Hawaiian Electric, Parent | PCB Contamination
Public Utilities, General Disclosures [Line Items]
Valuation allowances and reserves	9.7
Hawaiian Electric, Parent | Kapolei Petroleum Contamination | James Campbell Company
Public Utilities, General Disclosures [Line Items]
Environmental remediation expense	0.8
Hawaiian Electric, Parent | ERP/EAM Implementation Project
Public Utilities, General Disclosures [Line Items]
Regulatory liability for O&M expense reductions	3.3
Hawaii Electric Light Company, Inc | ERP/EAM Implementation Project
Public Utilities, General Disclosures [Line Items]
Regulatory liability for O&M expense reductions	3.3
Maui Electric
Public Utilities, General Disclosures [Line Items]
Additional accrued investigation and estimated cleanup costs	2.6
Maui Electric | ERP/EAM Implementation Project
Public Utilities, General Disclosures [Line Items]
Regulatory liability for O&M expense reductions	$ 4.9
Regulatory liability, amortization period	5 years