Electric utility segment - Utility Projects (Details) $ in Millions		1 Months Ended
	Jan. 31, 2024 USD ($)	Sep. 30, 2020 MW	Dec. 31, 2023 USD ($)	Aug. 29, 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
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			$ 24.7
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			$ 0.6
Climate Adaptation Transmission And Distribution Resilience Program | Hawaiian Electric Company, Inc. and Subsidiaries | Subsequent Event
Public Utilities, General Disclosures [Line Items]
Electric grid project, approved funds	$ 189.7
Electric grid project, period (in years)	5 years