Electric utility segment - Condensed consolidating statement of cash flows (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Cash flows from operating activities
Net cash provided by operating activities	$ 197,383	$ 133,406
Cash flows from investing activities
Capital expenditures	(197,816)	(229,282)
Other	4,469	6,143
Net cash used in investing activities	(629,256)	(275,130)
Cash flows from financing activities
Common stock dividends	(72,037)	(69,720)
Proceeds from issuance of short-term debt	(119,211)	112,901
Proceeds from issuance of long-term debt	351,942	56,150
Repayment of short-term debt	(100,000)	0
Repayment of long-term debt and funds transferred for repayment of long-term debt	(177,245)	(52,489)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(20,135)	1,445
Other	(1,672)	1,189
Net cash provided by financing activities	808,046	171,065
Net increase in cash, cash equivalents and restricted cash	376,173	29,341
Cash, cash equivalents and restricted cash, beginning of period	227,685	169,208
Cash, cash equivalents and restricted cash, end of period	603,858	198,549
Less: Restricted cash	(29,376)	0	$ (30,872)
Cash and cash equivalents, end of period	574,482	198,549	196,813
Consolidating adjustments
Cash flows from operating activities
Net cash provided by operating activities	(15,407)	(12,624)
Cash flows from investing activities
Capital expenditures	0	0
Advances from affiliates	(22,200)	30,300
Other	55	0
Net cash used in investing activities	(22,145)	30,300
Cash flows from financing activities
Common stock dividends	15,352	12,624
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	0	0
Repayment of short-term debt	0
Repayment of long-term debt and funds transferred for repayment of long-term debt	0	0
Net increase (decrease) in other bank borrowings with original maturities of three months or less	22,200	(30,300)
Other	0	0
Net cash provided by financing activities	37,552	(17,676)
Net increase 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
Cash and cash equivalents, end of period	0		0
Hawaiian Electric (parent only) | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	154,967	84,427
Cash flows from investing activities
Capital expenditures	(129,829)	(150,945)
Advances from affiliates	14,200	(25,300)
Other	4,354	2,821
Net cash used in investing activities	(111,275)	(173,424)
Cash flows from financing activities
Common stock dividends	(53,568)	(50,626)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(540)	(540)
Proceeds from issuance of short-term debt	100,000	25,000
Proceeds from issuance of long-term debt	205,000	30,000
Repayment of short-term debt	(100,000)
Repayment of long-term debt and funds transferred for repayment of long-term debt	(95,000)	(31,546)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(46,987)	116,901
Other	(1,039)	197
Net cash provided by financing activities	7,866	89,386
Net increase in cash, cash equivalents and restricted cash	51,558	389
Cash, cash equivalents and restricted cash, beginning of period	32,988	16,732
Cash, cash equivalents and restricted cash, end of period	84,546	17,121
Less: Restricted cash	(29,376)		(30,749)
Cash and cash equivalents, end of period	55,170		2,239
HELCO
Cash flows from financing activities
Repayment of long-term debt and funds transferred for repayment of long-term debt	(14,000)
HELCO | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	20,307	16,406
Cash flows from investing activities
Capital expenditures	(30,785)	(18,083)
Advances from affiliates	8,000	(5,000)
Other	552	(280)
Net cash used in investing activities	(22,233)	(23,363)
Cash flows from financing activities
Common stock dividends	(8,160)	(5,090)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(267)	(267)
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	10,000	10,000
Repayment of short-term debt	0
Repayment of long-term debt and funds transferred for repayment of long-term debt		(10,000)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	12,000	0
Other	(61)	43
Net cash provided by financing activities	(488)	(5,314)
Net increase in cash, cash equivalents and restricted cash	(2,414)	(12,271)
Cash, cash equivalents and restricted cash, beginning of period	7,008	15,623
Cash, cash equivalents and restricted cash, end of period	4,594	3,352
Less: Restricted cash	0		(123)
Cash and cash equivalents, end of period	4,594		6,885
Maui Electric
Cash flows from financing activities
Repayment of long-term debt and funds transferred for repayment of long-term debt	0
Maui Electric | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by operating activities	21,601	12,607
Cash flows from investing activities
Capital expenditures	(25,918)	(30,868)
Advances from affiliates	0	0
Other	480	(31)
Net cash used in investing activities	(25,438)	(30,899)
Cash flows from financing activities
Common stock dividends	(7,192)	(7,534)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(191)	(191)
Proceeds from issuance of short-term debt	0	0
Proceeds from issuance of long-term debt	40,000	10,000
Repayment of short-term debt	0
Repayment of long-term debt and funds transferred for repayment of long-term debt		(10,000)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(26,200)	25,300
Other	(247)	83
Net cash provided by financing activities	6,170	17,658
Net increase in cash, cash equivalents and restricted cash	2,333	(634)
Cash, cash equivalents and restricted cash, beginning of period	1,797	3,421
Cash, cash equivalents and restricted cash, end of period	4,130	2,787
Less: Restricted cash	0		0
Cash and cash equivalents, end of period	4,130		1,797
Other subsidiaries
Cash flows from financing activities
Repayment of long-term debt and funds transferred for repayment of long-term debt	0
Other subsidiaries | Reportable Legal Entities
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	0
Net cash used in investing activities	0	0
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	0
Proceeds from issuance of long-term debt	0	0
Repayment of short-term debt	0
Repayment of long-term debt and funds transferred for repayment of long-term debt		0
Net increase (decrease) 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 increase in cash, cash equivalents and restricted cash	0	0
Cash, cash equivalents and restricted cash, beginning of period	101	101
Cash, cash equivalents and restricted cash, end of period	101	101
Less: Restricted cash	0		0
Cash and cash equivalents, end of period	101		101
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net cash provided by operating activities	181,468	100,816
Cash flows from investing activities
Capital expenditures	(186,532)	(199,896)
Advances from affiliates	0	0
Other	5,441	2,510
Net cash used in investing activities	(181,091)	(197,386)
Cash flows from financing activities
Common stock dividends	(53,568)	(50,626)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(998)	(998)
Proceeds from issuance of short-term debt	100,000	25,000
Proceeds from issuance of long-term debt	255,000	50,000
Repayment of short-term debt	(100,000)	0
Repayment of long-term debt and funds transferred for repayment of long-term debt	(109,000)	(51,546)
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(38,987)	111,901
Other	(1,347)	323
Net cash provided by financing activities	51,100	84,054
Net increase in cash, cash equivalents and restricted cash	51,477	(12,516)
Cash, cash equivalents and restricted cash, beginning of period	41,894	35,877
Cash, cash equivalents and restricted cash, end of period	93,371	23,361
Less: Restricted cash	(29,376)	0	(30,872)
Cash and cash equivalents, end of period	$ 63,995	$ 23,361	$ 11,022