Electric utility segment - Purchases from IPPs (Details) - Hawaiian Electric, Parent - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 160	$ 153
Kalaeloa
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	66	67
HPOWER
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	17	18
Puna Geothermal Venture
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	13	8
Hamakua Energy
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	11	20
Kapolei Energy Storage
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	6	0
Wind IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	30	24
Solar IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	15	14
Other IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power		$ 2
Other Independent Power Producers, Including Netting
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 2