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Retirement benefits - Changes in Projected Benefit Obligations and Fair Value of Plan Assets and Amounts Recognized in OCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined benefit pension and other postretirement benefit plans liability	$ (60,671)	$ (49,748)
Pension benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	1,856,765	2,644,639
Service cost	45,578	78,173	$ 81,432
Interest cost	103,000	80,062	75,361
Actuarial loss (gain)	131,437	(848,905)
Participants contributions	0	0
Benefits paid and expenses	(103,802)	(97,204)
Benefit obligation, balance at the end of the period	2,032,978	1,856,765	2,644,639
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,806,379	2,320,745
Actual return on plan assets	260,748	(461,669)
Employer contributions	8,274	42,542
Participants contributions	0	0
Benefits paid and expenses	(101,862)	(95,239)
Fair value of plan assets, balance at the end of the period	1,973,539	1,806,379	2,320,745
Accrued benefit asset (liability), balance	(59,439)	(50,386)
Other assets	23,091	21,012
Defined benefit pension and other postretirement benefit plans liability	(82,530)	(71,398)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	74,418	347,799
Recognized during year – prior service credit	0	0
Recognized during year – net actuarial gain (loss)	(669)	(27,412)
Occurring during year – net actuarial loss (gain)	11,513	(245,969)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	85,262	74,418	347,799
Cumulative impact of PUC D&Os	(67,732)	(55,201)
AOCI debit/(credit), balance at end of the period	17,530	19,217
Net actuarial loss (gain)	85,262	74,418
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	85,262	74,418	347,799
Income taxes (benefits)	(4,639)	(5,088)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	12,891	14,129
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	1,716,125	2,464,944
Service cost	44,143	75,845	79,463
Interest cost	95,351	74,363	70,235
Actuarial loss (gain)	126,846	(804,498)
Participants contributions	0	0
Benefits paid and expenses	(94,783)	(88,450)
Transfers	781	(6,079)
Benefit obligation, balance at the end of the period	1,888,463	1,716,125	2,464,944
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,665,880	2,142,617
Actual return on plan assets	246,976	(426,825)
Employer contributions	8,252	41,894
Participants contributions	0	0
Benefits paid and expenses	(94,332)	(87,952)
Other	509	(3,854)
Fair value of plan assets, balance at the end of the period	1,827,285	1,665,880	2,142,617
Accrued benefit asset (liability), balance	(61,178)	(50,245)
Other assets	0	0
Other liabilities (short-term)	(507)	(497)
Defined benefit pension and other postretirement benefit plans liability	(60,671)	(49,748)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	57,264	329,645
Recognized during year – prior service credit	0	0
Recognized during year – net actuarial gain (loss)	(28)	(26,358)
Occurring during year – net actuarial loss (gain)	12,103	(246,023)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	69,339	57,264	329,645
Cumulative impact of PUC D&Os	(67,732)	(55,201)
AOCI debit/(credit), balance at end of the period	1,607	2,063
Net actuarial loss (gain)	69,339	57,264
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	69,339	57,264	329,645
Income taxes (benefits)	(414)	(531)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	1,193	1,532
Other benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	157,436	218,151
Service cost	1,430	2,580	2,827
Interest cost	8,520	6,502	6,122
Actuarial loss (gain)	(13,867)	(60,283)
Participants contributions	3,542	3,348
Benefits paid and expenses	(13,718)	(12,862)
Benefit obligation, balance at the end of the period	143,343	157,436	218,151
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	190,547	239,311
Actual return on plan assets	25,926	(39,469)
Employer contributions	0	0
Participants contributions	3,542	3,348
Benefits paid and expenses	(12,643)	(12,643)
Fair value of plan assets, balance at the end of the period	207,372	190,547	239,311
Accrued benefit asset (liability), balance	64,029	33,111
Other assets	64,463	33,526
Defined benefit pension and other postretirement benefit plans liability	(434)	(415)
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	(26,238)	(19,975)
Recognized during year – prior service credit	875	928
Recognized during year – net actuarial gain (loss)	1,888	12
Occurring during year – net actuarial loss (gain)	(26,143)	(7,203)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(49,618)	(26,238)	(19,975)
Cumulative impact of PUC D&Os	43,066	19,486
AOCI debit/(credit), balance at end of the period	(6,552)	(6,752)
Net actuarial loss (gain)	(49,618)	(25,363)
Prior service gain	0	(875)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(49,618)	(26,238)	(19,975)
Income taxes (benefits)	1,689	1,740
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	(4,863)	(5,012)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	150,534	209,470
Service cost	1,415	2,554	2,802
Interest cost	8,143	6,227	5,875
Actuarial loss (gain)	(13,721)	(58,253)
Participants contributions	3,473	3,286
Benefits paid and expenses	(13,272)	(12,750)
Transfers	0	0
Benefit obligation, balance at the end of the period	136,572	150,534	209,470
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	187,494	235,525
Actual return on plan assets	25,529	(38,764)
Employer contributions	0	0
Participants contributions	3,473	3,286
Benefits paid and expenses	(12,356)	(12,541)
Other	0	(12)
Fair value of plan assets, balance at the end of the period	204,140	187,494	235,525
Accrued benefit asset (liability), balance	67,568	36,960
Other assets	67,568	36,960
Other liabilities (short-term)	0	0
Defined benefit pension and other postretirement benefit plans liability	0	0
Defined Benefit Plan, Amounts Recognized in Other Comprehensive Income [Roll Forward]
AOCI debit/(credit), balance at beginning of the period (excluding impact of PUC D&Os)	(25,402)	(20,231)
Recognized during year – prior service credit	872	925
Recognized during year – net actuarial gain (loss)	1,827	0
Occurring during year – net actuarial loss (gain)	(25,807)	(6,096)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(48,510)	(25,402)	(20,231)
Cumulative impact of PUC D&Os	43,066	19,486
AOCI debit/(credit), balance at end of the period	(5,444)	(5,916)
Net actuarial loss (gain)	(48,510)	(24,530)
Prior service gain	0	(872)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(48,510)	(25,402)	$ (20,231)
Income taxes (benefits)	1,402	1,523
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	$ (4,042)	$ (4,393)

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- Definition

Represents the beginning and ending balance of accumulated other comprehensive income related to retirement benefit plans, excluding the impact of public utilities commission decision and orders.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment and other expenses. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment and other expenses. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Defined Benefit Plan, Transfers Of Employees Between Entities

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Represents the accumulated other comprehensive income which has been impacted by public utilities commission decision and orders.

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Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount, before tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount, before tax, of accumulated other comprehensive (income) loss for cost (credit) of benefit change attributable to participants' prior service from plan amendment or plan initiation of defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount of increase (decrease) in plan assets of defined benefit plan from actual return (loss) determined by change in fair value of plan assets adjusted for contributions, benefit payments, and other expenses.

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Amount of gain (loss) from change in actuarial assumptions which (increases) decreases benefit obligation of defined benefit plan. Assumptions include, but are not limited to, interest, mortality, employee turnover, salary, and temporary deviation from substantive plan.

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Amount of asset (liability), recognized in statement of financial position, for defined benefit pension and other postretirement plans.

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Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

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Amount of contributions received by defined benefit plan from participant which increase benefit obligation.

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Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

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