Electric utility segment - Regulatory Proceedings (Details)					1 Months Ended			12 Months Ended
	Dec. 23, 2020 USD ($)	Sep. 15, 2020 agreement	Jun. 05, 2020 USD ($)	Apr. 27, 2017 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Feb. 28, 2019 USD ($)	Dec. 31, 2020 USD ($) MWh agreement	Dec. 31, 2019 USD ($) contract	Dec. 31, 2018 $ / kWh	Oct. 22, 2020	Jul. 09, 2020 entity
Regulatory Projects and Legal Obligations [Line Items]
Advanced Metering Infrastructure Utilization PIM, annual maximum reward					$ 2,000,000.0			$ 2,000,000.0
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Multi-year rate period	5 years
Customer dividend, negative adjustment percentage	0.22%
Savings commitment liability, annual rate	$ 6,610,000
ERP system benefits savings, liability	$ 3,900,000
Authorized ROE								9.50%
Actual return on equity, dead band percentage, above or below target								3.00%
Actual earnings, above or below dead band								1.50%
Percentage sharing between customers and utilities								0.5
Percentage sharing for any further difference								9
Threshold of capital expenditures in excess of customer contributions for qualification for major project interim recovery				$ 2,500,000
Major project interim recovery requested amount			$ 23,600,000				$ 19,800,000
Percentage cap on cost recovery						90.00%			90.00%		90.00%
Percentage of allowed project costs to flow through MPIR mechanism											100.00%
Target performance historical measurement period								10 years
Service reliability, maximum penalty, percent of return on equity								20.00%
Maximum penalty, pending adjusted amount								$ 6,800,000
Dead band percentage above or below target								3.00%
Call center performance, maximum penalty, percent								8.00%
Call center performance, maximum penalty, pending adjusted amount								$ 1,400,000
Call center performance, maximum penalty amount					900,000	$ 300,000
Performance incentive mechanism, savings calculation, energy price, renewable projects with storage capacity | $ / kWh										0.115
Performance incentive mechanism, savings calculation, energy price, renewable energy-only projects | $ / kWh										0.095
Performance incentive mechanism, savings calculation, incentive cap									$ 3,500,000
Number of contracts which qualified for incentives | contract									7
Public utility, incentives accrued						$ 1,700,000			$ 1,700,000
Number of grid service purchase agreements | entity												2
Number of power purchase agreements (PPAs) (in agreements) | agreement		8						4
Number of power purchase agreements qualifying for potential payout | agreement		1
Interpolated statutory RPS goal rate, years 2021 and 2022 | MWh								20
Interpolated statutory RPS goal rate, year 2023 | MWh								15
Interpolated statutory RPS goal rate, remainder of MRP | MWh								10
Penalty rate for failure to meet RPS targets (megawatt per hour) | MWh								20
Grid Services Procurement PIM, maximum reward					1,500,000			$ 1,500,000
Interconnection Approval PIM, annual maximum reward					3,000,000.0			3,000,000.0
Interconnection Approval PIM, annual maximum penalty					900,000			900,000
Low-to-Moderate Income Energy Efficiency PIM, rewards cap					$ 2,000,000.0			$ 2,000,000.0
Low-to-Moderate Income Energy Efficiency PIM, duration								3 years
Hawaiian Electric Company, Inc. and Subsidiaries | Schofield Generation Station
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount			19,200,000
Hawaiian Electric Company, Inc. and Subsidiaries | West Loch PV Project
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount			3,800,000
Hawaiian Electric Company, Inc. and Subsidiaries | Grid Modernization Strategy Phase 1 Project
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount			$ 600,000