Electric utility segment - Major Project Interim Recovery and Performance Incentive Mechanisms (Details) - Hawaiian Electric Company, Inc. and Subsidiaries				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 ($)	May 31, 2019 USD ($)	Feb. 28, 2019 USD ($)	Dec. 31, 2018 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / kWh
Regulatory Projects and Legal Obligations [Line Items]
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			$ 3,600,000			$ 19,800,000
Target performance historical measurement period									10 years
Service reliability, maximum penalty, percent of return on equity									0.20%
Maximum penalty, pending adjusted amount									$ 6,700,000
Dead band percentage above or below target									3.00%
Call center performance, maximum penalty, percent									0.80%
Call center performance, maximum penalty, pending adjusted amount									$ 1,300,000
Call center performance, maximum penalty amount				$ 300,000	$ 1,300,000		$ 2,100,000
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, expected savings percentage, phase 1										20.00%
Performance incentive mechanism, savings calculation, incentive cap								$ 3,000,000		$ 3,500,000
Performance incentive mechanism, expected savings in Phase 2, January 2019								15.00%
Performance incentive mechanism, expected savings in Phase 2, February 2019								10.00%
Performance incentive mechanism, expected savings in Phase 2, March 2019								5.00%
Performance incentive mechanism, penalty									$ 0
Number of contracts which qualified for incentives | contract		6
Public utility, incentives accrued								$ 1,700,000
Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	$ 24,200,000
Schofield Generation Station | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	19,200,000
West Loch PV Project | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	4,500,000
Grid Modernization Strategy Phase 1 Project | Subsequent Event
Regulatory Projects and Legal Obligations [Line Items]
Major project interim recovery requested amount	$ 500,000