Cash flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Continuing Operations
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	$ 131	$ 109	$ 94
Interest paid on finance lease obligations	31	6	1
Income taxes paid (net of refundable credits)	32	24	32
Income taxes refunded (including refundable credits)	0	1	2
Supplemental disclosures of noncash activities
Electric utility property, plant and equipment-Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	43	43	67
Common stock dividends reinvested in HEI common stock (financing)	0	5	0
Right-of-use assets obtained in exchange for operating lease obligations (investing)	2	0	47
Property, plant, equipment and other assets received in exchange for the assumption of debt associated with a business acquisition (investing)	0	0	68
Debt, lease liabilities and other liabilities assumed in business acquisition (financing)	0	0	68
Common stock issued (gross) for director and executive/management compensation (financing)	2	6	9
Right-of-use assets obtained in exchange for finance lease obligations (financing)	106	294	48
Discontinued Operations
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	121	61	12
Income taxes paid (net of refundable credits)	4	4	9
Income taxes refunded (including refundable credits)	2	0	0
Supplemental disclosures of noncash activities
Electric utility property, plant and equipment-Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	0	0	1
Right-of-use assets obtained in exchange for operating lease obligations (investing)	5	1	4
Common stock issued (gross) for director and executive/management compensation (financing)	1	2	1
Sale of ASB (investing/financing)	(508)	0	0
Loans transferred from held for investment to held for sale (investing)	29	106	0
Transfer of retail repurchase agreements to deposit liabilities (financing)	0	98	0
Obligations to fund low income housing investments, net (investing)	0	18	9
Transfer of securities from available for sale to held to maturities (investing)	0	0	755
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	88	74	69
Interest paid on finance lease obligations	31	6	1
Income taxes paid (net of refundable credits)	59	39	67
Income taxes refunded (including refundable credits)	0	2	0
Supplemental disclosures of noncash activities
Electric utility property, plant and equipment-Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	42	42	64
Right-of-use assets obtained in exchange for operating lease obligations (investing)	2	0	44
Right-of-use assets obtained in exchange for finance lease obligations (financing)	105	294	48
Estimated fair value of noncash contributions in aid of construction (investing)	19	21	14
Increase related to an acquisition (investing)	$ 0	$ 0	$ 15