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Electric utility segment - Additional Information (Details) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 Months Ended | 3 Months Ended | 12 Months Ended | 15 Months Ended | 17 Months Ended | 18 Months Ended |
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Feb. 16, 2018 USD ($) | Feb. 14, 2018 USD ($) | Jan. 19, 2018 USD ($) | Dec. 15, 2017 USD ($) | Nov. 15, 2017 | Oct. 12, 2017 USD ($) | Aug. 21, 2017 USD ($) | Jul. 11, 2017 | Apr. 27, 2017 USD ($) | Dec. 16, 2016 USD ($) | Sep. 19, 2016 USD ($) | Aug. 11, 2016 USD ($) | May 23, 2016 | Feb. 18, 2016 contract | Jan. 05, 2016 USD ($) | Jun. 30, 2017 USD ($) $ / kWh | Jul. 31, 2016 MW | Sep. 30, 2015 USD ($) | Jun. 30, 2015 MW | Aug. 31, 2012 MW | May 31, 2012 MW | Oct. 31, 2004 MW | Oct. 31, 1988 MW | Mar. 31, 1988 MW | Jun. 30, 2017 USD ($) | Mar. 31, 2017 USD ($) | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) MW agreement contract | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2017 USD ($) | Dec. 18, 2017 USD ($)
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |
Revenue subject to refund |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,000,000 |  |  |  |  |  |
Renewable projects |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ERP/EAM implementation project costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 35,300,000 |  |
ERP/EAM cost recovery cap |  |  |  |  |  |  |  |  |  |  |  | $ 77,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ERP/EAM required pass-through savings |  |  |  |  |  |  |  |  |  |  |  | $ 244,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 244,000,000
ERP/EAM project service period (in years) |  |  |  |  |  |  |  |  |  |  |  | 12 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average AFUDC rate |  |  |  |  |  |  |  |  |  |  |  | 1.75% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ERP/EAM estimated total benefits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 256,000,000
ERP/EAM implementation project costs, operations and management |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,700,000 |  |
ERP/EAM implementation project costs, capital costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2,600,000 |  |
ERP/EAM implementation project costs, deferred costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 26,000,000 |  |
Project facility capacity (in mW) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum project budget |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 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 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Project, lease term (in years) |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 35 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total project costs incurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 121,600,000 |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar project, energy production (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar project, project cap |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 67,000,000 |  |  |  |  |  |  |  |  | $ 67,000,000 |  |  |  |  |  |  |  |  |
Solar project, maximum energy costs (in dollars per KWH) | $ / kWh |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9.56 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Solar project, cost incurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 6,400,000 |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 263,209,000 | $ 237,950,000 |  | 263,209,000 | 263,209,000 | 263,209,000 |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Target performance historical measurement period |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Service reliability, maximum penalty, percent of return on equity |  |  |  |  |  |  |  |  | 0.20% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Maximum penalty amount |  |  |  |  |  |  |  |  | $ 6,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dead band percentage above or below target |  |  |  |  |  |  |  |  | 3.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Call center performance, maximum penalty amount |  |  |  |  |  |  |  |  | $ 1,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Threshold of capital expenditures in excess of customer contributions for qualification for major project interim recovery |  |  |  |  |  |  |  |  | $ 2,500,000.0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General rate increase, revenue |  |  |  |  |  |  |  |  |  | $ 106,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumption, rate of return |  |  |  |  |  |  |  |  |  | 8.28% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, return on average common equity |  |  |  |  | 9.75% |  |  |  |  | 10.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling order, requirement for application for general rate case |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 years |  |  |  |  |  |
Stipulated settlement letter, basis spread on reduction amount |  |  |  |  | 0.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stipulated settlement letter, perent of pass-through of minor energy generation fuel recovery |  |  |  |  | 100.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statement of probable entitlement, calculation assumptions, rate of return |  |  |  | 7.57% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statement of probable entitlement, calculation assumptions, rate of return, ROACE |  |  |  | 9.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, common equity capitalization |  |  |  | 57.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim D&O, reduction in revenue requirement, pension regulatory asset |  |  |  | $ 6,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim D&O, reduction in revenue requirement, pension contribution regulatory asset |  |  |  | 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim D&O, reduction in revenue requirement, pension contribution regulatory asset in 2011 |  |  |  | 17,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim D&O, reduction in revenue requirement, baseline plant additions |  |  |  | $ 5,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
PCB Contamination |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accrual for environmental loss contingencies |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,800,000 |  |  | 4,800,000 | 4,800,000 | 4,800,000 |
Biodiesel Fuel |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3 |  |  |  |  |  |
Chevron |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | contract |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Pacific Biodiesel Technologies | Biodiesel Fuel |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |
REG Marketing & Logistics | Biodiesel Fuel |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | contract |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |
Power purchase agreement, extension period (in years) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1 year |  |  |  |  |  |
AES Hawaii, Inc. (AES Hawaii) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase commitment, period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 30 years |  |  |  |  |  |  |  |  |  |
Purchase commitment, minimum power volume required to be purchased | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 186 |  |  |  | 180 |  |  |  |  |  |  |  |  |  |
Purchase commitment, arbitration, additional capacity requirement | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 9 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hu Honua Bioenergy |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Purchase commitment, minimum power volume required to be purchased | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 21.5 |  |  |  |  |  |  |  |  |  |  |  |  |
Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 22,300,000 |  |  | 22,300,000 | 22,300,000 | 22,300,000 |
Allowance for doubtful accounts receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4,900,000 |  |  | 4,900,000 | 4,900,000 | 4,900,000 |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fuel contracts |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated cost of minimum purchase within 2018 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 130,000,000 |  |  |  |  |  |
Estimated cost of minimum purchase in 2019 year |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 130,000,000 |  |  |  |  |  |
Cost of purchases |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 600,000,000 | 400,000,000 | $ 600,000,000 |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase capacity excluding agreements with smaller IPPs (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 551 |  |  |  |  |  |
Expected fixed capacity charges per year for 2018 through 2022, minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 100,000,000 |  |  |  |  |  |
Expected fixed capacity charges from 2023 through 2033 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 900,000,000 |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
ARO, recognition impact on earnings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |
Changes in the asset retirement obligation liability |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Balance at the beginning of the period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 25,589,000 | $ 6,035,000 | 25,589,000 | 26,848,000 |  |  |  |  |
Accretion expense |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10,000 | 10,000 |  |  |  |  |
Liabilities incurred |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5,370,000 | 0 |  |  |  |  |
Liabilities settled |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (527,000) | (1,269,000) |  |  |  |  |
Revisions in estimated cash flows |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | (24,407,000) | 0 |  |  |  |  |
Balance at the end of the period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,035,000 | $ 25,589,000 | $ 26,848,000 | 6,035,000 | 6,035,000 | 6,035,000 |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling, revision in estimated cash flows |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,000,000 | $ 12,000,000 |  | $ 20,000,000 |  |  |  |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated income tax expense (benefit) resulting from Tax Act |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 28,000,000 |  |  |  |  |  |  |
Hawaiian Electric Company, Inc (HECO) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of power purchase agreements (PPAs) | agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |
Hawaiian Electric Company, Inc (HECO) | Kalaeloa Partners, L.P. (Kalaeloa) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreements |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Power purchase capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 180 |  |  |  |  |  |  |  |  |  |  |
Number of years entity entered under power purchase agreement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 25 years |  |  |  |  |  |  |  |  |  |  |
Power purchase capacity that Increases from initial capacity (in megawatts) | MW |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 208 |  |  |  |  |  |  |  |  |  |  |  |
Power purchase agreement, termination period |  |  |  |  |  |  |  |  |  |  |  |  | 60 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Hawaiian Electric Company, Inc (HECO) | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 15,000,000 |  |  | 15,000,000 | 15,000,000 | 15,000,000 |
HELCO |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General rate increase, revenue |  |  |  |  |  |  |  |  |  |  | $ 19,300,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumption, rate of return |  |  |  |  |  |  |  |  |  |  | 8.44% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, return on average common equity |  |  |  |  |  |  |  |  |  |  | 10.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stipulated return on average common equity rate |  |  |  |  |  |  | 9.50% | 9.75% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General rate increase, return on average common equity percent decrease |  |  |  |  |  |  |  | 0.25% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Interim general rate increase |  |  |  |  |  |  | $ 9,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
HELCO | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated income tax expense (benefit) resulting from Tax Act |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,600,000 |  |  |  |  |  |  |
HELCO | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,000,000 |  |  | 6,000,000 | 6,000,000 | 6,000,000 |
MECO |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General rate increase, revenue |  |  |  |  |  | $ 30,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumption, rate of return |  |  |  |  |  | 8.05% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, return on average common equity |  |  |  |  |  | 10.60% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, common equity capitalization |  |  |  |  |  | 56.90% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
General rate increase, revenue, percent |  |  |  |  |  | 9.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions rate base |  |  |  |  |  | $ 473,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conditional general rate increase amount |  |  |  |  |  | $ 46,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Conditional general rate increase, revenue |  |  |  |  |  | 14.30% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
MECO | Scenario, Forecast |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Estimated income tax expense (benefit) resulting from Tax Act |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 2,500,000 |  |  |  |  |  |  |
MECO | Hawaiian Telcom |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Accounts receivable and unbilled revenues, net |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 1,300,000 |  |  | 1,300,000 | 1,300,000 | 1,300,000 |
Maui Electric Company, Limited (MECO) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Environmental regulation |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Additional accrued investigation and estimated cleanup costs |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,000,000 |  |  | $ 3,000,000 | $ 3,000,000 | $ 3,000,000 |
Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Decoupling |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statement of probable entitlement, interim increase | $ 36,000,000 | $ 15,600,000 | $ 36,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statement of probable entitlement, calculation assumptions, rate of return |  |  | 7.57% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Statement of probable entitlement, calculation assumptions, rate of return, ROACE |  |  | 9.50% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stipulated settlement letter, rate of return ROACE |  | 9.75% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Revenue, calculation assumptions, rate of return, common equity capitalization |  |  | 57.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition Represents the entity's aggregate capacity utilized under power purchase agreements (PPAs) excluding power purchase agreements with smaller independent power producers and schedule Q providers. + References No definition available. + Details
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- Definition Represents the entity's aggregate capacity utilized under power purchase agreements (PPAs). + References No definition available. + Details
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Namespace Prefix: | he_
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Balance Type: | na
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- Definition Aggregate of Power Purchase Capacity Increases from Initial Capacity + References No definition available. + Details
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- Definition Represents the amount of impact on earnings from recognition of asset retirement obligations (AROs). + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
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- Definition Represents the actual cost of purchases. + References No definition available. + Details
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Namespace Prefix: | he_
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Balance Type: | debit
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- Definition Decoupling [Abstract] + References No definition available. + Details
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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:stringItemType
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- Definition The minimum estimated amount in the second year after the balance sheet date the entity agreed to spend under the long-term purchase commitment. + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
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- Definition The minimum estimated amount in the first year after the balance sheet date the entity agreed to spend under the long-term purchase commitment. + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:monetaryItemType
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- Definition Long Term Purchase Commitment, Arbitration, Additional Capacity Requirement + References No definition available. + Details
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Namespace Prefix: | he_
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- Definition Long-term Purchase Commitment, Extension Period + References No definition available. + Details
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Balance Type: | na
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- Definition Long-term Purchase Commitment, Minimum Power Volume Required + References No definition available. + Details
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Namespace Prefix: | he_
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- Definition Represents the number of firm power purchase agreements entered into, by the company. + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:integerItemType
Balance Type: | na
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- Definition Represents the number of years under which the entity has entered for power purchase agreement. + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:durationItemType
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- Definition Power Purchase Agreement, Termination Period + References No definition available. + Details
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Namespace Prefix: | he_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
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Data Type: | xbrli:stringItemType
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- Definition Public Utilities, Conditional General Rate Increase, Revenue + References No definition available. + Details
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- Definition Public Utilities, Conditional General Rate Increase, Revenue, Percentage + References No definition available. + Details
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- Definition Public Utilities, Decoupling Order, Requirement For Application For General Rate Case + References No definition available. + Details
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- Definition Public Utilities, ERP/EAM Implementation Project Costs + References No definition available. + Details
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- Definition Public Utilities, ERP/EAM Implementation Project Costs, Capital Costs + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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- Definition Public Utilities, ERP/EAM Implementation Project Costs, Deferred Costs + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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- Definition Public Utilities, ERP/EAM Implementation Project Costs, Operations And Management + References No definition available. + Details
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Data Type: | xbrli:monetaryItemType
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- Definition Public Utilities, General Rate Increase, Agreement Revision, Percent Of Pass Through Of Minor Energy Generation Fuel Recovery + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Base + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Of Return + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Of Return, Common Equity Capitalization Percentage + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Of Return, Return On Average Common Equity + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Of Return, Return On Average Common Equity, Basis Spread On Reduction Amount + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Calculation Assumptions, Rate Of Return, Return On Average Common Equity, Percentage Decrease + References No definition available. + Details
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- Definition Public Utilities, General Rate Increase, Revenue, Percent + References No definition available. + Details
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- Definition Public Utilities, Interim Decision And Order, Reduction In Revenue Requirement, Baseline Plant Additions + References No definition available. + Details
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- Definition Public Utilities, Interim Decision And Order, Reduction In Revenue Requirement Of Pension Contribution Regulatory Asset + References No definition available. + Details
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- Definition Public Utilities, Interim Decision And Order, Reduction In Revenue Requirement Of Pension Contribution Regulatory Asset Established In 2011 + References No definition available. + Details
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- Definition Public Utilities, Interim Decision And Order, Reduction In Revenue Requirement Of Pension Regulatory Asset + References No definition available. + Details
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- Definition Public Utilities, Interim General Rate Increase + References No definition available. + Details
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- Definition Public Utilities, Solar Project, Cost Incurred + References No definition available. + Details
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- Definition Public Utilities, Solar Project, Facility Energy Production + References No definition available. + Details
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- Definition Public Utilities, Solar Project, Maximum Energy Cost + References No definition available. + Details
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- Definition Public Utilities, Solar Project, Project Cap + References No definition available. + Details
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- Definition Public Utilities, Statement Of Probable Entitlement, Interim Increase + References No definition available. + Details
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- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 410 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Asset Retirement Obligation -URI http://asc.fasb.org/extlink&oid=6505190 + Details
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