Electric utility segment - Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income (loss)	$ 248,056	$ 199,714	$ 219,772
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	246,158	238,114	229,858
Other amortization	32,544	52,664	48,255
Deferred income taxes	(5,398)	(1,706)	(15,085)
Allowance for equity funds used during construction	(9,534)	(8,768)	(11,987)
Other	(7,060)	1,366	18,568
Changes in assets and liabilities
Increase in fuel oil stock	(45,819)	34,202	(11,493)
Decrease (increase) in regulatory assets	(13,874)	1,007	71,262
Increase (decrease) in regulatory liabilities	15,358	(16,562)	1,953
Change in prepaid and accrued income taxes, tax credits and revenue taxes	41,331	(35,610)	(27,538)
Decrease in defined benefit pension and other postretirement benefit plans liability	(6,660)	(2,029)	(4,482)
Net cash provided by operating activities	375,673	429,407	512,470
Cash flows from investing activities
Capital expenditures	(314,524)	(383,895)	(457,520)
Other	27	3,412	13,291
Net cash used in investing activities	(1,179,592)	(1,413,648)	(541,709)
Cash flows from financing activities
Common stock dividends	(148,643)	(144,096)	(139,463)
Proceeds from issuance of long-term debt	285,886	415,997	289,349
Repayment of long-term debt	(82,262)	(178,969)	(287,285)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	(10,493)	(71,219)	86,718
Net increase (decrease) in other bank borrowings with original maturities of three months or less	(1,365)	(25,440)	5,070
Proceeds from issuance of short-term debt	0	165,000	75,000
Repayment of short-term debt	(65,000)	(150,000)	(50,000)
Other	(3,080)	(3,203)	(1,836)
Net cash used in financing activities	756,402	1,115,535	87,716
Net increase (decrease) in cash and equivalents	(47,517)	131,294	58,477
Cash, cash equivalents and restricted cash, January 1	358,979	227,685	169,208
Cash, cash equivalents and restricted cash, December 31	311,462	358,979	227,685
Less: Restricted cash	(5,911)	(17,558)	(30,872)
Cash and cash equivalents	305,551	341,421	196,813
Hawaiian Electric (parent only)
Cash flows from operating activities
Net income (loss)	246,166	197,824	217,882
Adjustments to reconcile net income to net cash provided by operating activities
Depreciation of property, plant and equipment	414	485	570
Changes in assets and liabilities
Net cash provided by operating activities	154,151	134,363	131,120
Cash flows from investing activities
Capital expenditures	(10)	(20)	(47)
Other	180	2,435	(1,001)
Net cash used in investing activities	(76,062)	(17,530)	(41,170)
Cash flows from financing activities
Common stock dividends	(148,643)	(144,096)	(139,463)
Proceeds from issuance of long-term debt	150,000	50,000	0
Repayment of long-term debt	(50,000)	0	0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	(10,493)	(32,232)	47,731
Proceeds from issuance of short-term debt	0	65,000	0
Repayment of short-term debt	(15,000)	(50,000)	0
Other	(1,767)	(459)	(10)
Net cash used in financing activities	(77,909)	(117,487)	(92,739)
Net increase (decrease) in cash and equivalents	180	(654)	(2,789)
Cash, cash equivalents and restricted cash, January 1	299	953	3,742
Cash, cash equivalents and restricted cash, December 31	479	299	953
Hawaiian Electric Company, Inc. and Subsidiaries
Cash flows from operating activities
Net income (loss)	179,637	171,335	158,835
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	0	0	(37)
Common stock dividends received from subsidiaries	0	0	35
Depreciation of property, plant and equipment	229,469	222,733	215,731
Other amortization	21,737	33,746	29,631
Deferred income taxes	(3,829)	3,151	(16,284)
State refundable credit	(10,582)	(9,961)	(8,369)
Bad debt expense	2,183	2,115	2,150
Allowance for equity funds used during construction	(9,534)	(8,768)	(11,987)
Bill credits	2,000	0	0
Accrued environmental reserve	0	6,556	406
Other	1,350	2,610	27,459
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(50,090)	(7,286)	18,822
Decrease (increase) in accrued unbilled revenues	(27,464)	15,285	4,495
Increase in fuel oil stock	(45,840)	33,699	(12,002)
Decrease (increase) in materials and supplies	(4,533)	(6,642)	(5,498)
Decrease (increase) in regulatory assets	(13,874)	1,007	71,262
Increase (decrease) in regulatory liabilities	15,358	(16,562)	1,953
Increase in accounts payable	17,671	(33,129)	(2,051)
Change in prepaid and accrued income taxes, tax credits and revenue taxes	26,930	(37,180)	(28,523)
Decrease in defined benefit pension and other postretirement benefit plans liability	(5,154)	(4,306)	(4,448)
Changes in other assets and liabilities	(52,302)	(31,852)	(17,624)
Net cash provided by operating activities	273,133	336,551	423,956
Cash flows from investing activities
Capital expenditures	(292,000)	(350,864)	(419,898)
Advances from (to) affiliates	0	0	0
Other	6,035	6,070	11,374
Net cash used in investing activities	(285,965)	(344,794)	(408,524)
Cash flows from financing activities
Common stock dividends	(111,700)	(107,134)	(101,252)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(1,995)	(1,995)	(1,995)
Proceeds from issuance of common stock	54,400	34,000	35,500
Proceeds from issuance of long-term debt	115,000	255,000	280,000
Repayment of long-term debt	0	(109,000)	(283,546)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	0	(38,987)	38,987
Net increase (decrease) in other bank borrowings with original maturities of three months or less		(38,987)
Proceeds from issuance of short-term debt	0	100,000	75,000
Repayment of short-term debt	(50,000)	(100,000)	(50,000)
Other	(941)	(2,209)	(2,109)
Net cash used in financing activities	4,764	29,675	(9,415)
Net increase (decrease) in cash and equivalents	(8,068)	21,432	6,017
Cash, cash equivalents and restricted cash, January 1	63,326	41,894	35,877
Cash, cash equivalents and restricted cash, December 31	55,258	63,326	41,894
Less: Restricted cash	(3,089)	(15,966)	(30,872)
Cash and cash equivalents	52,169	47,360	11,022
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaiian Electric (parent only)
Cash flows from operating activities
Net income (loss)	178,722	170,420	157,920
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	(45,353)	(47,504)	(43,204)
Common stock dividends received from subsidiaries	29,700	30,704	32,783
Depreciation of property, plant and equipment	155,607	151,387	143,470
Other amortization	16,688	24,511	23,351
Deferred income taxes	(3,191)	2,130	(13,547)
State refundable credit	(7,120)	(6,668)	(6,245)
Bad debt expense	1,159	1,042	1,236
Allowance for equity funds used during construction	(7,734)	(7,335)	(9,955)
Bill credits	1,400
Accrued environmental reserve		6,556	406
Other	366	1,201	27,575
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(41,727)	(8,093)	24,150
Decrease (increase) in accrued unbilled revenues	(18,345)	8,832	4,902
Increase in fuel oil stock	(32,407)	30,226	(14,741)
Decrease (increase) in materials and supplies	(3,220)	(3,910)	(4,585)
Decrease (increase) in regulatory assets	(15,422)	8,526	55,494
Increase (decrease) in regulatory liabilities	16,269	(5,490)	102
Increase in accounts payable	9,828	(26,093)	4,687
Change in prepaid and accrued income taxes, tax credits and revenue taxes	21,217	(25,757)	(24,900)
Decrease in defined benefit pension and other postretirement benefit plans liability	(3,480)	(3,092)	(3,033)
Changes in other assets and liabilities	(36,733)	(21,124)	(15,747)
Net cash provided by operating activities	216,224	280,469	340,119
Cash flows from investing activities
Capital expenditures	(194,984)	(229,127)	(311,538)
Advances from (to) affiliates	25,700	1,000	(27,700)
Other	(29,596)	(14,340)	5,241
Net cash used in investing activities	(198,880)	(242,467)	(333,997)
Cash flows from financing activities
Common stock dividends	(111,700)	(107,134)	(101,252)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(1,080)	(1,080)	(1,080)
Proceeds from issuance of common stock	54,400	34,000	35,500
Proceeds from issuance of long-term debt	60,000	205,000	190,000
Repayment of long-term debt		(95,000)	(183,546)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	0		46,987
Net increase (decrease) in other bank borrowings with original maturities of three months or less		(46,987)
Proceeds from issuance of short-term debt		100,000	75,000
Repayment of short-term debt	(50,000)	(100,000)	(50,000)
Other	(702)	(1,618)	(1,475)
Net cash used in financing activities	(49,082)	(12,819)	10,134
Net increase (decrease) in cash and equivalents	(31,738)	25,183	16,256
Cash, cash equivalents and restricted cash, January 1	58,171	32,988	16,732
Cash, cash equivalents and restricted cash, December 31	26,433	58,171	32,988
Less: Restricted cash	(3,089)	(15,966)	(30,749)
Cash and cash equivalents	23,344	42,205	2,239
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaii Electric Light
Cash flows from operating activities
Net income (loss)	21,714	28,027	21,351
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	0	0	0
Common stock dividends received from subsidiaries	0	0	0
Depreciation of property, plant and equipment	40,201	39,041	41,812
Other amortization	3,532	5,090	4,810
Deferred income taxes	(1,955)	(463)	(2,383)
State refundable credit	(1,672)	(1,593)	(559)
Bad debt expense	509	620	470
Allowance for equity funds used during construction	(586)	(543)	(816)
Bill credits	300
Accrued environmental reserve		0	0
Other	(41)	1,322	(61)
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(6,832)	(3,349)	2,858
Decrease (increase) in accrued unbilled revenues	(5,816)	3,327	(22)
Increase in fuel oil stock	(4,343)	430	2,126
Decrease (increase) in materials and supplies	169	(1,583)	(1,158)
Decrease (increase) in regulatory assets	24	(2,908)	9,218
Increase (decrease) in regulatory liabilities	(1,031)	(4,489)	(1,558)
Increase in accounts payable	4,723	(1,819)	(3,160)
Change in prepaid and accrued income taxes, tax credits and revenue taxes	3,861	(5,483)	(893)
Decrease in defined benefit pension and other postretirement benefit plans liability	(950)	(643)	(762)
Changes in other assets and liabilities	(5,833)	(8,864)	(6,152)
Net cash provided by operating activities	45,974	46,120	65,121
Cash flows from investing activities
Capital expenditures	(50,516)	(64,346)	(49,811)
Advances from (to) affiliates	0	8,000	(8,000)
Other	1,072	1,032	297
Net cash used in investing activities	(49,444)	(55,314)	(57,514)
Cash flows from financing activities
Common stock dividends	(14,600)	(16,320)	(17,680)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(534)	(534)	(534)
Proceeds from issuance of common stock	8,803	7,500	0
Proceeds from issuance of long-term debt	30,000	10,000	72,500
Repayment of long-term debt		(14,000)	(70,000)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	(17,800)		0
Net increase (decrease) in other bank borrowings with original maturities of three months or less		18,800
Proceeds from issuance of short-term debt		0	0
Repayment of short-term debt	0	0	0
Other	(119)	(214)	(508)
Net cash used in financing activities	5,750	5,232	(16,222)
Net increase (decrease) in cash and equivalents	2,280	(3,962)	(8,615)
Cash, cash equivalents and restricted cash, January 1	3,046	7,008	15,623
Cash, cash equivalents and restricted cash, December 31	5,326	3,046	7,008
Less: Restricted cash	0	0	(123)
Cash and cash equivalents	5,326	3,046	6,885
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Maui Electric
Cash flows from operating activities
Net income (loss)	24,554	20,392	22,731
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	0	0	0
Common stock dividends received from subsidiaries	0	0	0
Depreciation of property, plant and equipment	33,661	32,305	30,449
Other amortization	1,517	4,145	1,470
Deferred income taxes	1,317	1,484	(354)
State refundable credit	(1,790)	(1,700)	(1,565)
Bad debt expense	515	453	444
Allowance for equity funds used during construction	(1,214)	(890)	(1,216)
Bill credits	300
Accrued environmental reserve		0	0
Other	1,025	87	(55)
Changes in assets and liabilities
Decrease (increase) in accounts receivable	(3,071)	(1,343)	3,029
Decrease (increase) in accrued unbilled revenues	(3,303)	3,126	(385)
Increase in fuel oil stock	(9,090)	3,043	613
Decrease (increase) in materials and supplies	(1,482)	(1,149)	245
Decrease (increase) in regulatory assets	1,524	(4,611)	6,550
Increase (decrease) in regulatory liabilities	120	(6,583)	3,409
Increase in accounts payable	3,120	(5,217)	(3,578)
Change in prepaid and accrued income taxes, tax credits and revenue taxes	1,938	(5,998)	(3,097)
Decrease in defined benefit pension and other postretirement benefit plans liability	(724)	(571)	(653)
Changes in other assets and liabilities	(8,196)	3,635	(6,940)
Net cash provided by operating activities	40,721	40,608	51,097
Cash flows from investing activities
Capital expenditures	(46,500)	(57,391)	(58,549)
Advances from (to) affiliates	0	0	0
Other	1,073	960	1,303
Net cash used in investing activities	(45,427)	(56,431)	(57,246)
Cash flows from financing activities
Common stock dividends	(15,100)	(14,384)	(15,068)
Preferred stock dividends of Hawaiian Electric and subsidiaries	(381)	(381)	(381)
Proceeds from issuance of common stock	24,597	11,000	4,900
Proceeds from issuance of long-term debt	25,000	40,000	17,500
Repayment of long-term debt		0	(30,000)
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	(7,900)		27,700
Net increase (decrease) in other bank borrowings with original maturities of three months or less		(19,800)
Proceeds from issuance of short-term debt		0	0
Repayment of short-term debt	0	0	0
Other	(120)	(377)	(126)
Net cash used in financing activities	26,096	16,058	4,525
Net increase (decrease) in cash and equivalents	21,390	235	(1,624)
Cash, cash equivalents and restricted cash, January 1	2,032	1,797	3,421
Cash, cash equivalents and restricted cash, December 31	23,422	2,032	1,797
Less: Restricted cash	0	0	0
Cash and cash equivalents	23,422	2,032	1,797
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Other subsidiaries
Cash flows from operating activities
Net income (loss)	0	0	0
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	0	0	0
Common stock dividends received from subsidiaries	0	0	0
Depreciation of property, plant and equipment	0	0	0
Other amortization	0	0	0
Deferred income taxes	0	0	0
State refundable credit	0	0	0
Bad debt expense	0	0	0
Allowance for equity funds used during construction	0	0	0
Bill credits	0
Accrued environmental reserve		0	0
Other	0	0	0
Changes in assets and liabilities
Decrease (increase) in accounts receivable	0	0	0
Decrease (increase) in accrued unbilled revenues	0	0	0
Increase in fuel oil stock	0	0	0
Decrease (increase) in materials and supplies	0	0	0
Decrease (increase) in regulatory assets	0	0	0
Increase (decrease) in regulatory liabilities
Increase in accounts payable	0	0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes	0	0	0
Decrease in defined benefit pension and other postretirement benefit plans liability	0	0	0
Changes in other assets and liabilities	0	0	0
Net cash provided by operating activities	0	0	0
Cash flows from investing activities
Capital expenditures	0	0	0
Advances from (to) affiliates	0	0	0
Other		(24)	0
Net cash used in investing activities	0	(24)	0
Cash flows from financing activities
Common stock dividends	0	0	0
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0	0
Proceeds from issuance of common stock	0	0	0
Proceeds from issuance of long-term debt	0	0	0
Repayment of long-term debt		0	0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	0		0
Net increase (decrease) in other bank borrowings with original maturities of three months or less		0
Proceeds from issuance of short-term debt		0	0
Repayment of short-term debt	0	0	0
Other	0	0	0
Net cash used in financing activities	0	0	0
Net increase (decrease) in cash and equivalents	0	(24)	0
Cash, cash equivalents and restricted cash, January 1	77	101	101
Cash, cash equivalents and restricted cash, December 31	77	77	101
Less: Restricted cash	0	0	0
Cash and cash equivalents	77	77	101
Hawaiian Electric Company, Inc. and Subsidiaries | Consolidating adjustments
Cash flows from operating activities
Net income (loss)	(45,353)	(47,504)	(43,167)
Adjustments to reconcile net income to net cash provided by operating activities
Equity in earnings of subsidiaries	45,353	47,504	43,167
Common stock dividends received from subsidiaries	(29,700)	(30,704)	(32,748)
Depreciation of property, plant and equipment	0	0	0
Other amortization	0	0	0
Deferred income taxes	0	0	0
State refundable credit	0	0	0
Bad debt expense	0	0	0
Allowance for equity funds used during construction	0	0	0
Bill credits	0
Accrued environmental reserve		0	0
Other	0	0	0
Changes in assets and liabilities
Decrease (increase) in accounts receivable	1,540	5,499	(11,215)
Decrease (increase) in accrued unbilled revenues	0	0	0
Increase in fuel oil stock	0	0	0
Decrease (increase) in materials and supplies	0	0	0
Decrease (increase) in regulatory assets	0	0	0
Increase (decrease) in regulatory liabilities
Increase in accounts payable	0	0	0
Change in prepaid and accrued income taxes, tax credits and revenue taxes	(86)	58	367
Decrease in defined benefit pension and other postretirement benefit plans liability	0	0	0
Changes in other assets and liabilities	(1,540)	(5,499)	11,215
Net cash provided by operating activities	(29,786)	(30,646)	(32,381)
Cash flows from investing activities
Capital expenditures	0	0	0
Advances from (to) affiliates	(25,700)	(9,000)	35,700
Other	33,486	18,442	4,533
Net cash used in investing activities	7,786	9,442	40,233
Cash flows from financing activities
Common stock dividends	29,700	30,704	32,748
Preferred stock dividends of Hawaiian Electric and subsidiaries	0	0	0
Proceeds from issuance of common stock	(33,400)	(18,500)	(4,900)
Proceeds from issuance of long-term debt	0	0	0
Repayment of long-term debt		0	0
Net increase (decrease) in short-term borrowings from non-affiliates and affiliate with original maturities of three months or less	25,700		(35,700)
Net increase (decrease) in other bank borrowings with original maturities of three months or less		9,000
Proceeds from issuance of short-term debt		0	0
Repayment of short-term debt	0	0	0
Other	0	0	0
Net cash used in financing activities	22,000	21,204	(7,852)
Net increase (decrease) in cash and equivalents	0	0	0
Cash, cash equivalents and restricted cash, January 1	0	0	0
Cash, cash equivalents and restricted cash, December 31	0	0	0
Less: Restricted cash	0	0	0
Cash and cash equivalents	$ 0	$ 0	$ 0