Electric utility segment - Public Utility, Measured under Performance (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2025 USD ($) MWh	Dec. 31, 2024 USD ($)
Regulatory Projects and Legal Obligations [Line Items]
Interconnection requirements study, (penalties) rewards		$ 0.0
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Transmission and distribution-caused, maximum penalty	$ 3.6
Transmission and distribution-caused, (penalties) rewards		(1.0)
Call center performance, maximum penalty or reward	$ 1.4
Call center, (penalties) rewards		0.0
Interpolated RPS rate goal, after year three (in dollars per MWh) | MWh	10
Failure to meet RPS targets, penalty rate (in dollars per MWh) | MWh	20
Renewable portfolio standard, (penalties) rewards		1.9
Interconnection approval, maximum reward	$ 3.0
Interconnection approval, maximum penalty	0.9
Interconnection approval, (penalties) rewards		2.4
Generated-caused, maximum penalties	1.0
Performance incentive mechanism, (penalties) rewards	$ 0.3	6.2
Hawaii Electric Light Company, Inc
Regulatory Projects and Legal Obligations [Line Items]
Phase 1 RFP, (penalties) rewards		0.2
Generation caused, (penalties) rewards		(0.1)
Collective shared savings mechanism, (penalties) rewards		2.8
Performance incentive mechanism, (penalties) rewards		3.4
Hawaiian Electric, Parent
Regulatory Projects and Legal Obligations [Line Items]
Collective shared savings mechanism, retained percentage	20.00%
Performance incentive mechanism, (penalties) rewards		2.5
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Phase 1 RFP, (penalties) rewards	$ 0.3
Performance incentive mechanism, (penalties) rewards		$ 0.3