Cash flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	$ 98	$ 98	$ 107
Income taxes paid (net of refundable credits)	41	32	56
Income taxes refunded (including refundable credits)	7	3	4
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	48	44	64
Loans transferred from held for investment to held for sale (investing)	61	0	0
Real estate transferred from property, plant and equipment to other assets held-for-sale (investing)	3	0	0
Right-of-use assets obtained in exchange for operating lease obligations (investing)	44	26	7
Common stock issued (gross) for director and executive/management compensation (financing)	7	16	5
Obligations to fund low income housing investments, net (investing)	36	25	11
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	71	65	68
Income taxes paid (net of refundable credits)	45	41	55
Income taxes refunded (including refundable credits)	5	3	4
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	43	41	62
Right-of-use assets obtained in exchange for operating lease obligations (investing)	44	17	2
Electric utility property, plant and equipment
Estimated fair value of noncash contributions in aid of construction (investing)	8	10	9
Reduction of long-term debt from funds previously transferred for repayment (financing)	$ 0	$ 82	$ 0