Electric utility segment - Utility Projects (Details) - Hawaiian Electric Company, Inc. and Subsidiaries			1 Months Ended
	Jun. 10, 2019 USD ($)	Aug. 11, 2016 USD ($)	Nov. 30, 2019 USD ($) $ / kWh MW	Dec. 31, 2019 USD ($)
ERP/EAM Implementation Project
Regulatory Projects and Legal Obligations [Line Items]
ERP/EAM cost recovery cap		$ 77,600,000
ERP/EAM required pass-through savings		$ 246,000,000
ERP/EAM project service period (in years)	12 years	12 years
Weighted average AFUDC rate		1.75%
ERP/EAM implementation project costs, accrued carrying costs once put into service				$ 59,300,000
ERP/EAM implementation project, expected future O&M expense reductions	$ 150,000,000
ERP/EAM implementation project, future cost avoidance related to capital costs and tax costs	$ 96,000,000
ERP/EAM regulatory liability for operation and maitenance expense reductions				2,400,000
West Loch PV Project
Regulatory Projects and Legal Obligations [Line Items]
Solar project, energy production (in megawatts) | MW			20
Solar project, project cap			$ 67,000,000
Solar project, maximum energy costs (in dollars per KWH) | $ / kWh			0.0956
Solar project, cost incurred				51,400,000
Federal nonrefundable tax credits				13,400,000
State nonrefundable tax credits				$ 14,000,000.0