Electric utility segment - Rate proceedings (Details) - USD ($) $ in Millions	Nov. 13, 2019	Aug. 21, 2019
Hawaiian Electric (parent only)
Regulatory Projects and Legal Obligations [Line Items]
General rate increase, revenue		$ 77.6
Stipulated ROACE rate		10.50%
General rate increase, revenue, percent		4.10%
Assumptions on rate of return, return on average common equity, percentage decrease		8.00%
HELCO
Regulatory Projects and Legal Obligations [Line Items]
Effective interest rate of return	7.52%
Stipulated ROACE rate	9.50%
Common equity capitalization rate	58.00%
Rate Base	$ 543.0
Interim revenue requirement	$ 387.0