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Electric utility segment - Utility projects (Details) | 1 Months Ended | 6 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | ---
Nov. 30, 2019 USD ($) MW | Jun. 30, 2022 USD ($) | Dec. 31, 2021 USD ($) | Nov. 30, 2021 USD ($) | Oct. 31, 2020 generationUnit transmission_line kV | Jun. 10, 2019 USD ($) | Oct. 31, 2018 USD ($)
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Operating lease right-of-use assets |  | $ 120,600,000 | $ 122,416,000 |  |  |  |
Federal |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Tax credit deferral period |  | 25 years |  |  |  |  |
State |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Tax credit deferral period |  | 10 years |  |  |  |  |
ERP/EAM Implementation Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Future O&M expense reductions |  |  |  |  |  | $ 150,000,000 |
Future cost avoidance related to capital cost and tax costs |  |  |  |  |  | $ 96,000,000 |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Operating lease right-of-use assets |  | $ 99,690,000 | $ 101,470,000 |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | ERP/EAM Implementation Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
ERP/EAM project service period (in years) |  | 12 years |  |  |  |  |
ERP/EAM project service, savings over 12 years |  |  |  |  |  |  | $ 246,000,000
Regulatory liability for O&M expense reductions |  | $ 9,600,000 |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | West Loch PV Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Solar project, energy production (in megawatts) | MW | 20 |  |  |  |  |  |
Solar project, project cap | $ 67,000,000 |  |  |  |  |  |
Solar project, project cap for in-kind work | $ 4,700,000 |  |  |  |  |  |
Solar project, cost incurred |  | 60,100,000 |  |  |  |  |
Federal nonrefundable tax credits |  | 14,700,000 |  |  |  |  |
State nonrefundable tax credits |  | 14,000,000 |  |  |  |  |
Operating lease right-of-use assets |  | 6,400,000 |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Waena Switchyard/Synchronous Condenser Project |  |  |  |  |  |  |
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 |  |  |  | $ 38,800,000 |  |  |
Renewable energy generation project, incurred cost |  | 10,200,000 |  |  |  |  |
Hawaiian Electric | PCB Contamination |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Valuation allowances and reserves |  | 10,100,000 |  |  |  |  |
Hawaiian Electric | ERP/EAM Implementation Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  | 4,800,000 |  |  |  |  |
Hawaii Electric Light | ERP/EAM Implementation Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  | 1,900,000 |  |  |  |  |
Maui Electric |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Additional accrued investigation and estimated cleanup costs |  | 2,700,000 |  |  |  |  |
Maui Electric | ERP/EAM Implementation Project |  |  |  |  |  |  |
Public Utilities, General Disclosures [Line Items] |  |  |  |  |  |  |
Regulatory liability for O&M expense reductions |  | $ 2,900,000 |  |  |  |  |
Regulatory liability, amortization period |  | 5 years |  |  |  |  |

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