Electric utility segment - Annual Decoupling Filings Summary (Details) - USD ($) $ in Millions		9 Months Ended
	Oct. 28, 2024	Sep. 30, 2024
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues		$ 22.9
Annual change in accrued RBA balance through September 30, 2024 (and associated revenue taxes)		(1.9)
Incremental PIMs (net)		0.0
Net incremental amount to be collected under the RBA rate tariffs		21.0
Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues	$ 22.9
Management Audit savings commitment	(6.6)
Net 2025 ARA revenues	16.3
Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues		15.4
Annual change in accrued RBA balance through September 30, 2024 (and associated revenue taxes)		(7.0)
Incremental PIMs (net)		(0.1)
Net incremental amount to be collected under the RBA rate tariffs		8.3
Hawaiian Electric, Parent | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues	15.4
Management Audit savings commitment	(4.6)
Net 2025 ARA revenues	10.8
Hawaii Electric Light
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues		3.8
Annual change in accrued RBA balance through September 30, 2024 (and associated revenue taxes)		(1.3)
Incremental PIMs (net)		0.1
Net incremental amount to be collected under the RBA rate tariffs		2.6
Hawaii Electric Light | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues	3.8
Management Audit savings commitment	(1.0)
Net 2025 ARA revenues	2.8
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues		3.7
Annual change in accrued RBA balance through September 30, 2024 (and associated revenue taxes)		6.4
Incremental PIMs (net)		0.0
Net incremental amount to be collected under the RBA rate tariffs		$ 10.1
Maui Electric | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
2025 ARA revenues	3.7
Management Audit savings commitment	(1.0)
Net 2025 ARA revenues	$ 2.7