Income taxes - Schedule of Reconciliation of Amount of Income Taxes Computed at Federal Statutory Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Income Tax Expense (Benefit) [Line Items]
Amount at the federal statutory income tax rate	$ (376,235)	$ 38,283	$ 42,410
Increase (decrease) resulting from:
State income taxes, net of federal income tax benefit	(85,483)	7,989	8,812
Net deferred tax asset (liability) adjustment related to the Tax Act	(6,200)	(7,316)	(9,886)
Tax credits, net	(2,987)	(2,251)	(487)
Other, net	(57)	(2,171)	(1,934)
Total	$ (470,962)	$ 34,534	$ 38,915
Effective income tax rate (%)	26.30%	18.90%	19.30%
Hawaiian Electric Company, Inc. and Subsidiaries
Income Tax Expense (Benefit) [Line Items]
Amount at the federal statutory income tax rate	$ (349,423)	$ 51,899	$ 50,526
Increase (decrease) resulting from:
State income taxes, net of federal income tax benefit	(79,487)	11,097	11,026
Net deferred tax asset (liability) adjustment related to the Tax Act	(6,200)	(7,316)	(9,886)
Tax credits, net	(2,987)	(2,251)	(397)
Other, net	(1,450)	(2,236)	(1,593)
Total	$ (439,547)	$ 51,193	$ 49,676
Effective income tax rate (%)	26.40%	20.70%	20.60%