Electric utility segment - Commitments and Contingencies (Details) $ in Millions		1 Months Ended			12 Months Ended
	Nov. 16, 2023 defendant	Jan. 31, 2024	Jul. 31, 2018 MW	May 31, 2012 MW	Dec. 31, 2024 USD ($) agreement contract MW
Regulatory Projects and Legal Obligations [Line Items]
Valuation allowances and reserves, statement of financial position, not disclosed					reserve account balance
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Additional accrued investigation and estimated cleanup costs | $					$ 2.5
Hawaiian Electric | PCB Contamination
Regulatory Projects and Legal Obligations [Line Items]
Valuation allowances and reserves | $					$ 9.5
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, minimum power volume required to be purchased					10.56
Notice period		60 days
Number of power purchase agreements (PPAs) | agreement					4
Power purchase capacity excluding agreements with smaller IPPs					368.7
Hu Honua Bioenergy
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, minimum power volume required to be purchased				21.5
Number of defendants | defendant	3
Molokai New Energy Partners
Regulatory Projects and Legal Obligations [Line Items]
Total contracted PV capacity (in megawatts)			4.88
Total contracted battery energy storage system capacity			3
Maximum power volume to be delivered (in megawatts)			2.64
Stage 1 And 2 Renewable PPAs | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, minimum power volume required to be purchased					219.5
Total contracted PV capacity (in megawatts)					1,443
Number of power purchase agreements (PPAs) | agreement					7
Long-term contract for purchase of electric power, estimated annual cost | $					$ 28.0
PPAs beginning commercial operations | contract					3