Electric utility segment - Regulatory Proceedings (Details)				3 Months Ended	12 Months Ended
	May 26, 2021 USD ($)	Dec. 23, 2020 USD ($)	Apr. 27, 2017 USD ($)	Nov. 30, 2021 agreement	Dec. 31, 2021 USD ($) MWh contract project	Dec. 31, 2019 USD ($) contract	Mar. 23, 2021 mechanism	Feb. 16, 2021 contract	Dec. 31, 2020 agreement	Jul. 09, 2020 agreement
Regulatory Projects and Legal Obligations [Line Items]
Pilot process annual cap		$ 10,000,000
PUC proposal period		45 days
Advanced metering infrastructure utilization PIM, annual maximum reward					$ 2,000,000
Advanced metering infrastructure utilization PIM, duration					3 years
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Multi-year rate period		5 years
Customer dividend, negative adjustment percentage		0.0022%
Savings commitment liability, annual rate		$ 6,600,000
ERP system benefits savings, liability		$ 3,900,000
Actual return on equity, dead band percentage, above or below target					3.00%
Authorized ROE					9.50%
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	$ 21,800,000
EPRM number of projects approved | contract					2
EPRM project costs					$ 41,000,000
EPRM number of projects | project					5
EPRM total project costs					$ 264,000,000
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
Service reliability, estimated penalties					$ 200,000
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
Number of contracts which qualified for incentives | contract						7
Public utility, incentives accrued					$ 100,000	$ 1,700,000
Number of grid service purchase agreements | agreement									2	2
Number of additional power purchase contracts | contract								1
Number of power purchase contracts approved | agreement				2
Number of performance incentive mechanisms | mechanism							2
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
RPS-A PIM estimated reward amount					$ 700,000
Penalty rate for failure to meet RPS targets (megawatt per hour) | MWh					20
Grid services procurement PIM, maximum reward					$ 1,500,000
Interconnection approval PIM, annual maximum reward					3,000,000
Interconnection approval PIM, annual maximum penalty					900,000
Interconnection approval PIM, accrued estimated rewards					2,800,000
Low-to-moderate income energy efficiency PIM, rewards cap					$ 2,000,000
Low-to-moderate income energy efficiency PIM, duration					3 years
Accrued estimated rewards, net of penalties					$ 3,400,000
Hawaiian Electric Company, Inc. and Subsidiaries | Schofield Generation Station
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	17,600,000
Hawaiian Electric Company, Inc. and Subsidiaries | West Loch PV Project
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	3,300,000
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	$ 900,000
Hawaiian Electric
Regulatory Projects and Legal Obligations [Line Items]
Accrued estimated rewards, net of penalties					2,600,000
HELCO
Regulatory Projects and Legal Obligations [Line Items]
Accrued estimated rewards, net of penalties					300,000
Maui Electric
Regulatory Projects and Legal Obligations [Line Items]
Accrued estimated rewards, net of penalties					$ 500,000