Electric utility segment - Regulatory Proceedings (Details)				1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 05, 2020 USD ($)	Feb. 07, 2020 USD ($)	Apr. 27, 2017 USD ($)	Dec. 31, 2019 USD ($)	Mar. 31, 2019 $ / kWh	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) entity	Jul. 09, 2020 entity
Regulatory Projects and Legal Obligations [Line Items]
Decoupling order, service reliability performance, historical measurement period (in years)						10 years
Service reliability, pending adjusted maximum penalty amount						$ 6,800,000
Dead band percentage above or below the target						3.00%
Call center performance, pending adjusted maximum penalty						$ 1,400,000
Energy price, renewable projects with storage capacity (in dollars per kilowatt hour) | $ / kWh					0.115
Energy price, renewable energy-only projects (in dollars per kilowatt hour) | $ / kWh					0.095
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Threshold of capital expenditures in excess of contributions			$ 2,500,000
MPIR requested amount		$ 23,600,000					$ 19,800,000
Maximum penalty, percent of ROE						0.20%
Call center performance, maximum penalty percentage						0.08%
Call center performance, maximum penalty amount				$ 300,000
Performance incentive mechanism, incentive cap							$ 3,500,000
Number of power purchase agreements (PPAs) (in agreements) | entity							7
Incentives accrued				$ 1,700,000			$ 1,700,000
Subsequent Event | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
Number of grid service purchase agreements | entity								2
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount	$ 600,000
Schofield Generation Station | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount		$ 19,200,000
West Loch PV Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount	$ 3,800,000