Cash flows (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Supplemental disclosures of cash flow information
Interest paid to non-affiliates	$ 46	$ 43
Income taxes paid (including refundable credits)	21	14
Income taxes refunded (including refundable credits)	0	45
Supplemental disclosures of noncash activities
Common stock dividends reinvested in HEI common stock (financing)	0	11
Loans transferred from held for investment to held for sale (investing)	9	0
Common stock issued (gross) for director and executive/management compensation (financing)	11	6
Estimated fair value of noncash contributions in aid of construction (investing)	2	8
Change in unpaid invoices and accruals for capital expenditures (investing)	(7)	(32)
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates	36	31
Income taxes paid (including refundable credits)	8	0
Income taxes refunded (including refundable credits)	0	20
Supplemental disclosures of noncash activities
Estimated fair value of noncash contributions in aid of construction (investing)	2	8
Change in unpaid invoices and accruals for capital expenditures (investing)	$ (7)	$ (32)