Cash flows (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	$ 10	$ 15
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	24	28
Increase related to an acquisition (investing)	15	0
Right-of-use assets obtained in exchange for operating lease obligations (investing)	35	28
Common stock issued (gross) for director and executive/management compensation (financing)	8	6
Unsettled trades to purchase investment securities (investing)	25	0
Other receivable related to pending sales proceeds from the sale of an equity-method investment (investing)	9	0
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	6	9
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	21	24
Increase related to an acquisition (investing)	15	0
Right-of-use assets obtained in exchange for operating lease obligations (investing)	$ 32	$ 28