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, 2024	Dec. 31, 2023	Dec. 31, 2022
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Defined benefit plans liability	$ 23,213	$ 78,200
Defined benefit plans liability	(23,213)	(78,200)
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Other assets (long-term)	108,819	67,568
Defined benefit plans liability	6,428	60,671
Defined benefit plans liability	(6,428)	(60,671)
Pension benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	2,032,978	1,856,765
Service cost	45,821	45,228	$ 77,823
Interest cost	101,882	98,606	76,817
Actuarial loss (gain)	(106,453)	130,280
Participants contributions	0	0
Benefits paid and expenses	(99,494)	(98,353)
Benefit obligation, balance at the end of the period	1,893,577	2,032,978	1,856,765
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,973,539	1,806,379
Actual return on plan assets	105,938	252,998
Employer contributions	8,778	8,274
Participants contributions	0	0
Benefits paid and expenses	(97,735)	(96,667)
Fair value of plan assets, balance at the end of the period	1,888,853	1,973,539	1,806,379
Accrued benefit asset (liability), balance	(4,724)	(59,439)
Accrued benefit asset (liability), December 31	(4,724)	(59,439)
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)	85,262	74,418
Recognized during year – prior service credit	0	0
Recognized during year – net actuarial gain (loss)	(359)	(182)
Occurring during year – net actuarial loss (gain)	(73,969)	12,471
Adjustment from discontinued operations	(11,897)	(1,445)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(963)	85,262	74,418
Cumulative impact of PUC D&Os	5,999	(67,732)
AOCI debit/(credit), balance at end of the period	5,036	17,530
Net actuarial loss (gain)	(963)	85,262
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(963)	85,262	74,418
Income taxes (benefits)	(1,297)	(4,639)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	3,739	12,891
Pension benefits | Continuing Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	1,951,821	1,776,060
Benefit obligation, balance at the end of the period	1,893,577	1,951,821	1,776,060
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,871,872	1,707,267
Fair value of plan assets, balance at the end of the period	1,888,853	1,871,872	1,707,267
Accrued benefit asset (liability), balance	(4,724)	(79,949)
Other assets (long-term)	20,269	0
Other liabilities (short-term)	(1,780)	(1,757)
Defined benefit plans liability	23,213	78,192
Accrued benefit asset (liability), December 31	(4,724)	(79,949)
Defined benefit plans liability	(23,213)	(78,192)
Pension benefits | Discontinued Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	81,157	80,705
Change in projected benefit obligations - discontinued operations	(81,157)	452
Benefit obligation, balance at the end of the period	0	81,157	80,705
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	101,667	99,112
Change in plan assets - discontinued operations	(101,667)	2,555
Fair value of plan assets, balance at the end of the period	0	101,667	99,112
Accrued benefit asset (liability), balance	0	20,510
Accrued benefit asset (liability), December 31	0	20,510
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	1,888,463	1,716,125
Service cost	44,669	44,143	75,845
Interest cost	98,492	95,351	74,363
Actuarial loss (gain)	(104,692)	126,846
Participants contributions	0	0
Benefits paid and expenses	(95,785)	(94,783)
Transfers	(693)	781
Benefit obligation, balance at the end of the period	1,830,454	1,888,463	1,716,125
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	1,827,285	1,665,880
Actual return on plan assets	103,457	246,976
Employer contributions	8,733	8,252
Participants contributions	0	0
Benefits paid and expenses	(95,261)	(94,332)
Other	(538)	509
Fair value of plan assets, balance at the end of the period	1,843,676	1,827,285	1,665,880
Accrued benefit asset (liability), balance	13,222	(61,178)
Other assets (long-term)	20,164	0
Other liabilities (short-term)	(514)	(507)
Defined benefit plans liability	6,428	60,671
Accrued benefit asset (liability), December 31	13,222	(61,178)
Defined benefit plans liability	(6,428)	(60,671)
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)	69,339	57,264
Recognized during year – prior service credit	0	0
Recognized during year – net actuarial gain (loss)	(99)	(28)
Occurring during year – net actuarial loss (gain)	(73,215)	12,103
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(3,975)	69,339	57,264
Cumulative impact of PUC D&Os	5,999	(67,732)
AOCI debit/(credit), balance at end of the period	2,024	1,607
Net actuarial loss (gain)	(3,975)	69,339
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(3,975)	69,339	57,264
Income taxes (benefits)	(522)	(414)
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	1,502	1,193
Other benefits
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	143,343	157,436
Service cost	1,112	1,430	2,580
Interest cost	7,365	8,497	6,488
Actuarial loss (gain)	(9,913)	(13,863)
Participants contributions	4,024	3,542
Benefits paid and expenses	(13,594)	(13,718)
Benefit obligation, balance at the end of the period	131,903	143,343	157,436
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	207,372	190,547
Actual return on plan assets	19,438	25,926
Employer contributions	0	0
Participants contributions	4,024	3,542
Benefits paid and expenses	(12,944)	(12,643)
Fair value of plan assets, balance at the end of the period	217,890	207,372	190,547
Accrued benefit asset (liability), balance	85,987	64,029
Accrued benefit asset (liability), December 31	85,987	64,029
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)	(49,618)	(26,238)
Recognized during year – prior service credit	0	875
Recognized during year – net actuarial gain (loss)	2,898	1,865
Occurring during year – net actuarial loss (gain)	(15,401)	(26,140)
Adjustment from discontinued operations	142	20
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(61,979)	(49,618)	(26,238)
Cumulative impact of PUC D&Os	55,140	43,066
AOCI debit/(credit), balance at end of the period	(6,839)	(6,552)
Net actuarial loss (gain)	(61,979)	(49,618)
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(61,979)	(49,618)	(26,238)
Income taxes (benefits)	1,761	1,689
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	(5,078)	(4,863)
Other benefits | Continuing Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	142,909	157,021
Benefit obligation, balance at the end of the period	131,903	142,909	157,021
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	207,372	190,547
Fair value of plan assets, balance at the end of the period	217,890	207,372	190,547
Accrued benefit asset (liability), balance	85,987	64,463
Other assets (long-term)	87,066	65,527
Other liabilities (short-term)	(1,079)	(1,064)
Defined benefit plans liability	0	0
Accrued benefit asset (liability), December 31	85,987	64,463
Defined benefit plans liability	0	0
Other benefits | Discontinued Operations
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Benefit obligation, balance at the beginning of the period	434	415
Change in projected benefit obligations - discontinued operations	(434)	19
Benefit obligation, balance at the end of the period	0	434	415
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	0	0
Change in plan assets - discontinued operations	0	0
Fair value of plan assets, balance at the end of the period	0	0	0
Accrued benefit asset (liability), balance	0	(434)
Accrued benefit asset (liability), December 31	0	(434)
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	136,572	150,534
Service cost	1,096	1,415	2,554
Interest cost	7,039	8,143	6,227
Actuarial loss (gain)	(9,688)	(13,721)
Participants contributions	3,951	3,473
Benefits paid and expenses	(12,835)	(13,272)
Transfers	(47)	0
Benefit obligation, balance at the end of the period	126,088	136,572	150,534
Defined Benefit Plan, Change in Fair Value of Plan Assets [Roll Forward]
Fair value of plan assets, balance at the beginning of the period	204,140	187,494
Actual return on plan assets	19,299	25,529
Employer contributions	0	0
Participants contributions	3,951	3,473
Benefits paid and expenses	(12,600)	(12,356)
Other	(47)	0
Fair value of plan assets, balance at the end of the period	214,743	204,140	187,494
Accrued benefit asset (liability), balance	88,655	67,568
Other assets (long-term)	88,655	67,568
Other liabilities (short-term)	0	0
Defined benefit plans liability	0	0
Accrued benefit asset (liability), December 31	88,655	67,568
Defined 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)	(48,510)	(25,402)
Recognized during year – prior service credit	0	872
Recognized during year – net actuarial gain (loss)	2,840	1,827
Occurring during year – net actuarial loss (gain)	(15,245)	(25,807)
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(60,915)	(48,510)	(25,402)
Cumulative impact of PUC D&Os	55,140	43,066
AOCI debit/(credit), balance at end of the period	(5,775)	(5,444)
Net actuarial loss (gain)	(60,915)	(48,510)
Prior service gain	0	0
AOCI debit/(credit), balance at end of the period (excluding impact of PUC D&Os)	(60,915)	(48,510)	$ (25,402)
Income taxes (benefits)	1,487	1,402
AOCI debit/(credit), net of taxes (benefits) balance at the end of the period	$ (4,288)	$ (4,042)