Electric utility segment - Regulatory Assets for COVID-19 Related Costs (Details) - Hawaiian Electric Company, Inc. and Subsidiaries - USD ($) $ in Millions		1 Months Ended		9 Months Ended
	Jun. 09, 2022	Jun. 30, 2022	Dec. 31, 2021	Sep. 30, 2023
Regulatory Projects and Legal Obligations [Line Items]
Recovery of deferral costs	$ 27.8	$ 27.8
Recovery of deferral costs period (in years)	3 years	3 years
COVID-19
Regulatory Projects and Legal Obligations [Line Items]
Customer bill forgiveness			$ 2.0
Public utilities in regulatory assets				$ 8.8