Electric utility segment - Regulatory Proceedings (Details)				1 Months Ended			3 Months Ended	12 Months Ended
	Feb. 07, 2020 USD ($)	Mar. 25, 2019 contract	Apr. 27, 2017 USD ($)	Dec. 31, 2019 USD ($)	May 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / kWh	Aug. 31, 2019 USD ($)
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
Call center performance, maximum penalty amount						$ 2,100,000
Call center, additional penalty accrued					$ 1,300,000
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
Expected savings, phase 1, percent									20.00%
Performance incentive mechanism, incentive cap								$ 3,000,000	$ 3,500,000
Expected savings, Phase 2, January 2019									15.00%
Expected savings, Phase 2, February 2019									10.00%
Expected savings, Phase 2, March 2019									5.00%
Performance incentive mechanism penalty									$ 0
Number of contracts which qualified for incentives under Phase 1 | contract		6
Incentives accrued										$ 12,900
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	$ 24,200,000							$ 19,800,000	$ 3,600,000
Maximum penalty, percent of ROE							0.20%
Call center performance, maximum penalty percentage							0.08%
Call center performance, maximum penalty amount				$ 300,000
Grid Modernization Strategy Phase 1 Project | Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory Projects and Legal Obligations [Line Items]
MPIR requested amount	500,000
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	$ 4,500,000