Cash flows (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	$ 104	$ 59
Income taxes paid (including refundable credits)	28	26
Income taxes refunded (including refundable credits)	1	2
Supplemental disclosures of noncash activities
Estimated fair value of noncash contributions in aid of construction (investing)	9	6
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	45	34
Increase related to an acquisition (investing)	0	15
Right-of-use assets obtained in exchange for finance lease obligations (financing)	76	48
Right-of-use assets obtained in exchange for operating lease obligations (investing)	1	48
Property, plant, equipment and other assets received in exchange for the assumption of debt associated with a business acquisition (investing)	0	68
Debt, lease liabilities and other liabilities assumed in business acquisition (financing)	0	68
Common stock issued (gross) for director and executive/management compensation (financing)	8	10
Obligations to fund low income housing investments (investing)	7	9
Loans transferred from held for investment to held for sale (investing)	95	0
Transfer of retail repurchase agreements to deposit liabilities (financing)	98	0
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	45	40
Income taxes paid (including refundable credits)	38	46
Income taxes refunded (including refundable credits)	2	0
Supplemental disclosures of noncash activities
Estimated fair value of noncash contributions in aid of construction (investing)	9	6
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	43	31
Increase related to an acquisition (investing)	0	15
Right-of-use assets obtained in exchange for finance lease obligations (financing)	76	48
Right-of-use assets obtained in exchange for operating lease obligations (investing)	$ 0	$ 44