Electric utility segment - Annual decoupling filings summary (Details) - USD ($) $ in Millions		9 Months Ended
	Oct. 31, 2022	Sep. 30, 2022
Regulatory Projects and Legal Obligations [Line Items]
Incremental RAM revenues and ARA revenues		$ 40.1
Annual change in accrued RBA balance		(13.5)
Incremental Performance Incentive Mechanisms (net)		0.4
Incremental MPIR/EPRM Revenue Adjustment		0.3
Net incremental amount to be collected under the RBA rate tariffs		27.3
Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	$ 40.1
Management Audit savings commitment	(6.6)
Net 2023 ARA revenues	33.5
Hawaiian Electric
Regulatory Projects and Legal Obligations [Line Items]
Incremental RAM revenues and ARA revenues		27.0
Annual change in accrued RBA balance		(3.6)
Incremental Performance Incentive Mechanisms (net)		0.3
Incremental MPIR/EPRM Revenue Adjustment		0.3
Net incremental amount to be collected under the RBA rate tariffs		24.0
Hawaiian Electric | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	27.0
Management Audit savings commitment	(4.6)
Net 2023 ARA revenues	22.4
Hawaii Electric Light
Regulatory Projects and Legal Obligations [Line Items]
Incremental RAM revenues and ARA revenues		6.6
Annual change in accrued RBA balance		(6.7)
Incremental Performance Incentive Mechanisms (net)		0.1
Incremental MPIR/EPRM Revenue Adjustment		0.0
Net incremental amount to be collected under the RBA rate tariffs		0.0
Hawaii Electric Light | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	6.6
Management Audit savings commitment	(1.0)
Net 2023 ARA revenues	5.6
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Incremental RAM revenues and ARA revenues		6.5
Annual change in accrued RBA balance		(3.2)
Incremental Performance Incentive Mechanisms (net)		0.0
Incremental MPIR/EPRM Revenue Adjustment		0.0
Net incremental amount to be collected under the RBA rate tariffs		$ 3.3
Maui Electric | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2023 ARA revenues	6.5
Management Audit savings commitment	(1.0)
Net 2023 ARA revenues	$ 5.5