Electric utility segment - Purchases from IPPs (Details) - Hawaiian Electric, Parent - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 189	$ 178	$ 530	$ 499
Kalaeloa
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	74	77	219	211
HPOWER
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	20	17	53	51
Puna Geothermal Venture
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	15	7	42	24
Hamakua Energy
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	9	13	25	52
Kapolei Energy Storage
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	6	0	18	0
Wind IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	37	42	104	99
Solar IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	26	21	62	57
Other IPPs
Regulatory Projects and Legal Obligations [Line Items]
Purchased power	$ 2	$ 1	$ 7	$ 5