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Electric utility segment - Utility Projects (Details) $ in Millions |  | 9 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Sep. 01, 2023 USD ($) | Sep. 30, 2023 USD ($) | Dec. 31, 2022 USD ($) | Nov. 30, 2021 USD ($) | Oct. 31, 2020 transmission_line generationUnit kV
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Environmental loss contingency, statement of financial position, not disclosed |  | reserve account balance |  |  |
Maui Electric |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Additional accrued investigation and estimated cleanup costs |  | $ 2.6 |  |  |
Hawaiian Electric, Parent | PCB Contamination |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Valuation allowances and reserves |  | 9.7 |  |  |
Hawaiian Electric, Parent | Kapolei Petroleum Contamination | James Campbell Company |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Environmental remediation expense | $ 1.2 |  | $ 0.8 |  |
Waena Switchyard/Synchronous Condenser Project | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |
Number of extended transmission lines | transmission_line |  |  |  |  | 2
Number of kilovolts | kV |  |  |  |  | 69
Number of generating units converting to synchronous condensers | generationUnit |  |  |  |  | 2
Renewable energy generation project, approved funds |  |  |  | $ 38.8 |
Renewable energy generation project, incurred cost |  | $ 24.7 |  |  |

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