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Electric utility segment - Commitments and contingencies (Details) |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 6 Months Ended | 22 Months Ended |  |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
May 19, 2016 USD ($) kWh | Apr. 18, 2016 USD ($) | Feb. 18, 2016 | Jan. 05, 2016 USD ($) | Nov. 13, 2015 MW | Oct. 30, 2015 USD ($) | Oct. 26, 2015 USD ($) | Aug. 03, 2015 state | May 31, 2013 | Feb. 16, 2012 generation_unit | Nov. 30, 2015 USD ($) | Sep. 30, 2015 USD ($) | Jun. 30, 2015 USD ($) MW | May 31, 2015 USD ($) | Oct. 31, 2014 bidder | Aug. 31, 2014 | Jul. 31, 2014 USD ($) | Apr. 30, 2014 order | Feb. 28, 2013 bid | Aug. 31, 2012 MW | May 31, 2012 MW | Feb. 28, 2012 USD ($) | Mar. 31, 1988 MW | Jun. 30, 2016 USD ($) | Sep. 30, 2015 USD ($) | Jun. 30, 2016 USD ($) | Jun. 30, 2015 USD ($) | Dec. 31, 2013 USD ($) MW | Dec. 31, 2045 | Jul. 19, 2016 USD ($) | Dec. 31, 2015 USD ($) | Jun. 20, 2014 | Mar. 01, 2014 | Feb. 07, 2014
Regulatory projects and legal obligations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fuel supply contract term |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase commitment, period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |  |
Minimum power volume required | MW |  |  |  |  | 180 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 186 |  |  | 180 |  |  |  |  |  |  |  |  |  |  |
Additional capacity requirement | MW |  |  |  |  | 9 |  |  |  |  |  |  |  | 9 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Enterprise resource management system project, estimated costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 82,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Enterprise resource management system project, difference between Option A and B |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 20,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
SAP software costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,800,000 |  |  |  |  |  |  |  |  |
Schofield generating station facility capacity | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Schofield generating station project, budgetary cap |  |  |  | $ 157,300,000 |  |  |  |  |  |  |  | $ 167,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of costs recoverable through recovery mechanisms other than base rates |  |  |  |  |  |  |  |  |  |  |  | 90.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decrease in project costs |  |  |  | $ 9,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of EGUs impacted by proposed rules of MATS | generation_unit |  |  |  |  |  |  |  |  |  | 14 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental remediation expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 200,000 |  |  |  |  |  |  |  |
States included in interim state-wide emission limits | state |  |  |  |  |  |  |  | 48 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue requirement associated with plant additions |  | $ 35,700,000 |  |  |  |  | $ 40,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 224,179,000 |  | 224,179,000 |  |  |  |  | $ 242,766,000 |  |  |
Number of orders from regulatory agency | order |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percent of energy production from renewable energy sources |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 65.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Derivative measurement range |  |  |  | 30 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Designated as Hedging Instrument | Window forward contract | Cash Flow Hedging |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Notional amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20,637,000 |  | 20,637,000 |  |  |  |  | 0 |  |  |
Fair value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 466,000 |  | 466,000 |  |  |  |  | $ 0 |  |  |
Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Expected portfolio standard |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% |  |  |  |  |
Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 19,200,000 |  | 19,200,000 |  |  |  |  |  |  |  |
Accrued interest receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,500,000 |  | 3,500,000 |  |  |  |  |  |  |  |
Expected receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15,700,000 |  | 15,700,000 |  |  |  |  |  |  |  |
PCB Contamination |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Valuation allowances and reserves |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,500,000 |  | 4,500,000 |  |  |  |  |  |  |  |
US Fish and Wildlife Service |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental penalty expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 250 |  |  |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory projects and legal obligations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum deferred costs, inter-island projects |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 5,890,000 |  |  |  |  |  |  |  |  |  |  |  |
Maximum deferred cost recovery, contractor service costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,100,000 |  |  |  |  |  |
Integration from renewable energy sources (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 200 |  |  |  |  |  |
Maximum deferred cost recovery, contractor service costs, amortization period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |
Capacity integration from dispatchable renewable geothermal sources | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 |  |  |  |  |  |  |  |  |  |  |  |  |
Deferred cost recovery of geothermal dispatchable energy costs |  |  |  |  |  |  |  |  |  |  | $ 2,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of bids received | bid |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of eligible bidders | bidder |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of reduction in GHG emissions by 2020 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 16.00% |  |
Estimated annual fee for greenhouse gas emissions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 500,000 |  |  |  |  |  |  |  |
Impact on earnings from recognition of AROs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |
Changes in the asset retirement obligation liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance, beginning of period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 27,550,000 | 26,848,000 | $ 29,419,000 |  |  |  |  |  |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7,000 | 12,000 |  |  |  |  |  |  |
Liabilities incurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  |  |  |  |  |  |
Liabilities settled |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (259,000) | (1,881,000) |  |  |  |  |  |  |
Revisions in estimated cash flows |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 0 |  |  |  |  |  |  |
Balance, end of period |  |  |  |  |  |  |  |  |  |  |  |  | $ 27,550,000 |  |  |  |  |  |  |  |  |  |  | 26,596,000 |  | 26,596,000 | $ 27,550,000 |  |  |  |  |  |  |
Decoupling implementation experience, period |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed rate base adjustment, percent of previous rate base adjustment |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 90.00%
Effective interest rate, revenue balancing account |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.00%
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period to file required plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 120 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Changes in the asset retirement obligation liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed effective interest rate, revenue balancing account |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1.25% |
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Changes in the asset retirement obligation liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Proposed effective interest rate, revenue balancing account |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.25% |
Hawaiian Electric Company |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of extension resulting in MATS compliance date |  |  |  |  |  |  |  |  |  | 1 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual incremental RAM adjusted revenues | $ 11,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued earnings sharing credits | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes) | (13,600,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net annual incremental decrease in amount to be collected under the tariffs | (2,600,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impact on typical residential customer monthly bill | $ 0.01 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Monthly utility usage assumption (in kilowatts per hour) | kWh | 500 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hawaiian Electric Company | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 13,300,000 |  | 13,300,000 |  |  |  |  |  |  |  |
Hawaii Electric Light Company, Inc. (HELCO) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual incremental RAM adjusted revenues | $ 2,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued earnings sharing credits | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes) | (2,500,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net annual incremental decrease in amount to be collected under the tariffs | (200,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impact on typical residential customer monthly bill | $ 0.13 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Monthly utility usage assumption (in kilowatts per hour) | kWh | 500 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hawaii Electric Light Company, Inc. (HELCO) | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,600,000 |  | 5,600,000 |  |  |  |  |  |  |  |
Maui Electric |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional accrued investigation and estimated cleanup costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3,600,000 |  | 3,600,000 |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue requirement associated with plant additions |  |  |  |  |  | $ 4,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual incremental RAM adjusted revenues | $ 2,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued earnings sharing credits | 500,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes) | (4,300,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net annual incremental decrease in amount to be collected under the tariffs | (1,400,000) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impact on typical residential customer monthly bill | (0.95) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maui Electric | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 300,000 |  | $ 300,000 |  |  |  |  |  |  |  |
Lanai and Molokai |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Public Utilities, Phase-in Plans [Abstract] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Impact on typical residential customer monthly bill | $ (0.76) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Monthly utility usage assumption (in kilowatts per hour) | kWh | 400 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Regulatory projects and legal obligations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conversion of existing generating units to natural gas, costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 341,000,000 |  |  |  |
Liquefied natural gas containers cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 117,000,000 |  |  |  |
Construction of generation system at the Kahe power plant |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 859,000,000 |  |  |  |

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