Electric utility segment - Utility Projects (Details) $ in Millions		1 Months Ended	12 Months Ended
	Jan. 31, 2024 USD ($)	Sep. 30, 2020 MW	Dec. 31, 2024 USD ($)	Aug. 07, 2024 USD ($)	Dec. 31, 2023 USD ($)	Nov. 30, 2021 USD ($)	Oct. 31, 2020 generationUnit transmission_line kV
Hawaiian Electric Company, Inc. and Subsidiaries
Public Utilities, General Disclosures [Line Items]
Project cost recovery cap				$ 95.0
Project costs incurred			$ 9.7
Waena Switchyard/Synchronous Condenser Project | Hawaiian Electric Company, Inc. and Subsidiaries
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			$ 25.5
Waena Switchyard/Synchronous Condenser Project | Maui Electric
Public Utilities, General Disclosures [Line Items]
Mandatory retirement extension period			1 year
Waena Battery Energy Storage System Project
Public Utilities, General Disclosures [Line Items]
Total contracted battery energy storage system capacity | MW		40
Waena Battery Energy Storage System Project | Hawaiian Electric Company, Inc. and Subsidiaries
Public Utilities, General Disclosures [Line Items]
Renewable energy generation project, approved funds					$ 82.1
Renewable energy generation project, incurred cost			$ 6.7
Climate Adaptation Transmission And Distribution Resilience Program | Hawaiian Electric Company, Inc. and Subsidiaries
Public Utilities, General Disclosures [Line Items]
Electric grid project, approved funds	$ 189.7
Electric grid project, period (in years)	5 years