Electric utility segment - Purchases from IPPs (Details) - Hawaiian Electric, Parent - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 183	$ 189	$ 505	$ 530
Kalaeloa Partners, L.P.
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	73	74	201	219
HPOWER
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	16	20	55	53
Puna Geothermal Venture
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	12	15	31	42
Hamakua Energy
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	11	9	24	25
Kapolei Energy Storage
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	6	6	18	18
Wind IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	33	37	90	104
Solar IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	31	26	82	62
Other IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 1	$ 2	$ 4	$ 7