Income taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Expense (Benefit) [Line Items]
Amount at the federal statutory income tax rate	$ 65,281	$ 50,531	$ 56,996
Increase (decrease) resulting from:
State income taxes, net of federal income tax benefit	15,735	9,448	11,658
Net deferred tax asset (liability) adjustment related to the Tax Act	(9,886)	(11,267)	(9,255)
Other, net	(8,323)	(7,802)	(7,762)
Total	$ 62,807	$ 40,910	$ 51,637
Effective income tax rate	20.20%	17.00%	19.00%
Hawaiian Electric Company, Inc. and Subsidiaries
Income Tax Expense (Benefit) [Line Items]
Amount at the federal statutory income tax rate	$ 46,995	$ 44,468	$ 41,399
Increase (decrease) resulting from:
State income taxes, net of federal income tax benefit	10,323	9,658	8,703
Net deferred tax asset (liability) adjustment related to the Tax Act	(9,886)	(11,267)	(9,255)
Other, net	(3,284)	(2,441)	(2,542)
Total	$ 44,148	$ 40,418	$ 38,305
Effective income tax rate	19.70%	19.10%	19.40%