Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities
Net cash provided by operating activities	$ 267,205	$ 312,268
Cash flows from investing activities
Capital expenditures	(219,252)	(296,172)
Other	10,078	4,899
Net cash used in investing activities	(984,839)	(1,144,633)
Cash flows from financing activities
Common stock dividends	(111,477)	(108,066)
Proceeds from issuance of short-term debt	0	165,000
Repayment of short-term debt	(65,000)	(100,000)
Proceeds from issuance of long-term debt	206,988	365,146
Repayment of long-term debt	(80,607)	(178,291)
Net increase in other bank borrowings with original maturities of three months or less	39,635	6,765
Other	(7,462)	(7,275)
Net cash provided by financing activities	595,990	819,687
Net decrease in cash, cash equivalents and restricted cash	(121,644)	(12,678)
Cash, cash equivalents and restricted cash, beginning of period	358,979	227,685
Cash, cash equivalents and restricted cash, end of period	237,335	215,007
Less: Restricted cash	(9,412)	(21,881)	$ (17,558)
Cash and cash equivalents, end of period	227,923	193,126	341,421
Hawaiian Electric Consolidated
Cash flows from operating activities
Net cash provided by operating activities	198,256	244,955
Cash flows from investing activities
Capital expenditures	(203,746)	(267,482)
Advances from affiliates	0	0
Other	6,157	7,295
Net cash used in investing activities	(197,589)	(260,187)
Cash flows from financing activities
Common stock dividends	(83,775)	(80,352)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(1,496)	(1,496)
Proceeds from issuance of short-term debt	0	100,000
Repayment of short-term debt	(50,000)	(100,000)
Proceeds from issuance of long-term debt	115,000	255,000
Repayment of long-term debt	0	(109,000)
Net increase in other bank borrowings with original maturities of three months or less	0	(38,987)
Other	(942)	(1,569)
Net cash provided by financing activities	(21,213)	23,596
Net decrease in cash, cash equivalents and restricted cash	(20,546)	8,364
Cash, cash equivalents and restricted cash, beginning of period	63,326	41,894
Cash, cash equivalents and restricted cash, end of period	42,780	50,258
Less: Restricted cash	(6,313)	(20,458)	(15,966)
Cash and cash equivalents, end of period	36,467	29,800	47,360
Hawaiian Electric Consolidated | Reportable Legal Entities | Hawaiian Electric Industries, Inc.
Cash flows from operating activities
Net cash provided by operating activities	157,191	205,645
Cash flows from investing activities
Capital expenditures	(137,916)	(180,088)
Advances from affiliates	26,000	(800)
Other	4,136	5,636
Net cash used in investing activities	(107,780)	(175,252)
Cash flows from financing activities
Common stock dividends	(83,775)	(80,352)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(810)	(810)
Proceeds from issuance of short-term debt		100,000
Repayment of short-term debt	(50,000)	(100,000)
Proceeds from issuance of long-term debt	60,000	205,000
Repayment of long-term debt		(95,000)
Net increase in other bank borrowings with original maturities of three months or less	0	(46,987)
Other	(703)	(1,249)
Net cash provided by financing activities	(75,288)	(19,398)
Net decrease in cash, cash equivalents and restricted cash	(25,877)	10,995
Cash, cash equivalents and restricted cash, beginning of period	58,171	32,988
Cash, cash equivalents and restricted cash, end of period	32,294	43,983
Less: Restricted cash	(6,313)	(20,458)	(15,966)
Cash and cash equivalents, end of period	25,981	23,525	42,205
Hawaiian Electric Consolidated | Reportable Legal Entities | Hawaii Electric Light
Cash flows from operating activities
Net cash provided by operating activities	32,698	27,256
Cash flows from investing activities
Capital expenditures	(33,511)	(48,750)
Advances from affiliates	0	8,000
Other	1,121	1,056
Net cash used in investing activities	(32,390)	(39,694)
Cash flows from financing activities
Common stock dividends	(10,950)	(12,240)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(400)	(400)
Proceeds from issuance of short-term debt		0
Repayment of short-term debt	0	0
Proceeds from issuance of long-term debt	30,000	10,000
Repayment of long-term debt		(14,000)
Net increase in other bank borrowings with original maturities of three months or less	(18,100)	26,500
Other	(116)	(67)
Net cash provided by financing activities	434	9,793
Net decrease in cash, cash equivalents and restricted cash	742	(2,645)
Cash, cash equivalents and restricted cash, beginning of period	3,046	7,008
Cash, cash equivalents and restricted cash, end of period	3,788	4,363
Less: Restricted cash	0	0	0
Cash and cash equivalents, end of period	3,788	4,363	3,046
Hawaiian Electric Consolidated | Reportable Legal Entities | Maui Electric
Cash flows from operating activities
Net cash provided by operating activities	30,643	34,678
Cash flows from investing activities
Capital expenditures	(32,319)	(38,644)
Advances from affiliates	0	0
Other	900	1,031
Net cash used in investing activities	(31,419)	(37,613)
Cash flows from financing activities
Common stock dividends	(11,326)	(10,788)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(286)	(286)
Proceeds from issuance of short-term debt		0
Repayment of short-term debt	0	0
Proceeds from issuance of long-term debt	25,000	40,000
Repayment of long-term debt		0
Net increase in other bank borrowings with original maturities of three months or less	(7,900)	(25,700)
Other	(123)	(253)
Net cash provided by financing activities	5,365	2,973
Net decrease in cash, cash equivalents and restricted cash	4,589	38
Cash, cash equivalents and restricted cash, beginning of period	2,032	1,797
Cash, cash equivalents and restricted cash, end of period	6,621	1,835
Less: Restricted cash	0	0	0
Cash and cash equivalents, end of period	6,621	1,835	2,032
Hawaiian Electric Consolidated | Reportable Legal Entities | Other subsidiaries
Cash flows from operating activities
Net cash provided by operating activities	0	0
Cash flows from investing activities
Capital expenditures	0	0
Advances from affiliates	0	0
Other	0	(24)
Net cash used in investing activities	0	(24)
Cash flows from financing activities
Common stock dividends	0	0
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt		0
Repayment of short-term debt	0	0
Proceeds from issuance of long-term debt	0	0
Repayment of long-term debt		0
Net increase in other bank borrowings with original maturities of three months or less	0	0
Other	0	0
Net cash provided by financing activities	0	0
Net decrease in cash, cash equivalents and restricted cash	0	(24)
Cash, cash equivalents and restricted cash, beginning of period	77	101
Cash, cash equivalents and restricted cash, end of period	77	77
Less: Restricted cash	0	0	0
Cash and cash equivalents, end of period	77	77	77
Hawaiian Electric Consolidated | Consolidating adjustments
Cash flows from operating activities
Net cash provided by operating activities	(22,276)	(22,624)
Cash flows from investing activities
Capital expenditures	0	0
Advances from affiliates	(26,000)	(7,200)
Other	0	(404)
Net cash used in investing activities	(26,000)	(7,604)
Cash flows from financing activities
Common stock dividends	22,276	23,028
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt		0
Repayment of short-term debt	0	0
Proceeds from issuance of long-term debt	0	0
Repayment of long-term debt		0
Net increase in other bank borrowings with original maturities of three months or less	26,000	7,200
Other	0	0
Net cash provided by financing activities	48,276	30,228
Net decrease in cash, cash equivalents and restricted cash	0	0
Cash, cash equivalents and restricted cash, beginning of period	0	0
Cash, cash equivalents and restricted cash, end of period	0	0
Less: Restricted cash	0	0	0
Cash and cash equivalents, end of period	$ 0	$ 0	$ 0