Electric utility segment - Annual Decoupling Filings (Details) - USD ($) $ in Millions		12 Months Ended
	Oct. 31, 2022	Dec. 31, 2022
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	$ 40.1
Management Audit savings commitment	(6.6)
Net 2023 ARA revenues	33.5
Incremental ARA revenues		$ 40.1
Annual change in accrued RBA balance through September 30, 2022 (and associated revenue taxes)		(13.5)
Incremental EPRM/MPIR Revenue Adjustment		(0.1)
Incremental EPRM/MPIR Revenue Adjustment		0.3
Net incremental amount to be collected under the RBA rate tariffs		26.8
Hawaiian Electric
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	27.0
Management Audit savings commitment	(4.6)
Net 2023 ARA revenues	22.4
Incremental ARA revenues		27.0
Annual change in accrued RBA balance through September 30, 2022 (and associated revenue taxes)		(3.6)
Incremental EPRM/MPIR Revenue Adjustment		0.0
Incremental EPRM/MPIR Revenue Adjustment		0.3
Net incremental amount to be collected under the RBA rate tariffs		23.6
Hawaii Electric Light
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	6.6
Management Audit savings commitment	(1.0)
Net 2023 ARA revenues	5.6
Incremental ARA revenues		6.6
Annual change in accrued RBA balance through September 30, 2022 (and associated revenue taxes)		(6.7)
Incremental EPRM/MPIR Revenue Adjustment		0.0
Incremental EPRM/MPIR Revenue Adjustment		0.0
Net incremental amount to be collected under the RBA rate tariffs		(0.1)
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	6.5
Management Audit savings commitment	(1.0)
Net 2023 ARA revenues	$ 5.5
Incremental ARA revenues		6.5
Annual change in accrued RBA balance through September 30, 2022 (and associated revenue taxes)		(3.2)
Incremental EPRM/MPIR Revenue Adjustment		(0.1)
Incremental EPRM/MPIR Revenue Adjustment		0.0
Net incremental amount to be collected under the RBA rate tariffs		$ 3.3