Retirement benefits - Components of Net Periodic Benefit Cost for Consolidated HEI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Pension benefits
Defined Benefit Plan
Service cost	$ 10,900	$ 11,973	$ 30,796	$ 34,327
Interest cost	27,999	25,478	80,608	76,376
Expected return on plan assets	(33,845)	(34,606)	(101,558)	(103,800)
Amortization of net actuarial (gain)/losses	79	123	209	251
Net periodic pension/benefit cost (return)	5,133	2,968	10,055	7,154
Impact of PUC D&Os	15,200	17,406	50,799	53,585
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	20,333	20,374	60,854	60,739
Other benefits
Defined Benefit Plan
Service cost	245	270	741	833
Interest cost	1,819	1,803	5,461	5,525
Expected return on plan assets	(3,512)	(3,490)	(10,532)	(10,462)
Amortization of net actuarial (gain)/losses	(808)	(758)	(2,300)	(2,172)
Net periodic pension/benefit cost (return)	(2,256)	(2,175)	(6,630)	(6,276)
Impact of PUC D&Os	2,138	2,052	6,187	5,827
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	(118)	(123)	(443)	(449)
Hawaiian Electric Company, Inc. and Subsidiaries | Pension benefits
Defined Benefit Plan
Service cost	10,655	11,670	30,065	33,502
Interest cost	27,101	24,615	77,960	73,869
Expected return on plan assets	(33,041)	(33,769)	(99,142)	(101,321)
Amortization of net actuarial (gain)/losses	34	51	81	74
Net periodic pension/benefit cost (return)	4,749	2,567	8,964	6,124
Impact of PUC D&Os	15,200	17,406	50,799	53,585
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	19,949	19,973	59,763	59,709
Hawaiian Electric Company, Inc. and Subsidiaries | Other benefits
Defined Benefit Plan
Service cost	242	266	732	822
Interest cost	1,731	1,721	5,212	5,279
Expected return on plan assets	(3,464)	(3,438)	(10,387)	(10,306)
Amortization of net actuarial (gain)/losses	(811)	(742)	(2,285)	(2,130)
Net periodic pension/benefit cost (return)	(2,302)	(2,193)	(6,728)	(6,335)
Impact of PUC D&Os	2,138	2,052	6,187	5,827
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	$ (164)	$ (141)	$ (541)	$ (508)