Cash flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	$ 98,000	$ 107,000	$ 102,000
Income taxes paid (including refundable credits)	32,000	56,000	72,000
Income taxes refunded (including refundable credits)	3,000	4,000	34,000
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	44,000	64,000	59,000
Right-of-use assets obtained in exchange for operating lease obligations (investing)	26,000	7,000	0
Common stock issued (gross) for director and executive/management compensation (financing)	16,000	5,000	4,000
Obligations to fund low income housing investments, net (investing)	25,000	11,000	12,000
Transfer of retail repurchase agreements to deposit liabilities (financing)	0	0	102,000
Hawaiian Electric Company, Inc. and Subsidiaries
Supplemental disclosures of cash flow information
Interest paid to non-affiliates, net of amounts capitalized	65,000	68,000	73,000
Income taxes paid (including refundable credits)	41,000	55,000	64,000
Income taxes refunded (including refundable credits)	3,000	4,000	31,000
Supplemental disclosures of noncash activities
Unpaid invoices and accruals for capital expenditures, balance, end of period (investing)	41,000	62,000	44,000
Right-of-use assets obtained in exchange for operating lease obligations (investing)	17,000	2,000	0
Estimated fair value of noncash contributions in aid of construction (investing)	10,000	9,000	14,000
Acquisition of Hawaiian Telcom’s interest in joint poles (investing)	0	0	48,000
Reduction of long-term debt from funds previously transferred for repayment (financing)	$ 82,000	$ 0	$ 0