Retirement benefits - Components of Net Periodic Benefit Cost for Consolidated HEI (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Pension benefits
Defined Benefit Plan
Service cost	$ 12,061	$ 11,418	$ 34,590	$ 34,210
Interest cost	26,542	26,022	79,554	77,265
Expected return on plan assets	(35,993)	(35,238)	(107,957)	(105,630)
Amortization of net prior period gain	0	0	0	0
Amortization of net actuarial (gain)/losses	188	138	410	515
Net periodic pension/benefit cost (return)	2,798	2,340	6,597	6,360
Impact of PUC D&Os	17,406	17,663	53,585	53,929
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	20,204	20,003	60,182	60,289
Other benefits
Defined Benefit Plan
Service cost	270	385	833	1,072
Interest cost	1,808	2,075	5,542	6,389
Expected return on plan assets	(3,490)	(3,426)	(10,462)	(10,236)
Amortization of net prior period gain	0	(218)	0	(656)
Amortization of net actuarial (gain)/losses	(763)	(518)	(2,188)	(1,416)
Net periodic pension/benefit cost (return)	(2,175)	(1,702)	(6,275)	(4,847)
Impact of PUC D&Os	2,052	1,536	5,827	4,385
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	(123)	(166)	(448)	(462)
Hawaiian Electric Company, Inc. and Subsidiaries | Pension benefits
Defined Benefit Plan
Service cost	11,670	11,071	33,502	33,108
Interest cost	24,615	24,116	73,869	71,513
Expected return on plan assets	(33,769)	(33,029)	(101,321)	(98,972)
Amortization of net prior period gain	0	0	0	0
Amortization of net actuarial (gain)/losses	51	(16)	74	21
Net periodic pension/benefit cost (return)	2,567	2,142	6,124	5,670
Impact of PUC D&Os	17,406	17,663	53,585	53,929
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	19,973	19,805	59,709	59,599
Hawaiian Electric Company, Inc. and Subsidiaries | Other benefits
Defined Benefit Plan
Service cost	266	380	822	1,060
Interest cost	1,721	1,981	5,279	6,107
Expected return on plan assets	(3,438)	(3,374)	(10,306)	(10,081)
Amortization of net prior period gain	0	(218)	0	(654)
Amortization of net actuarial (gain)/losses	(742)	(503)	(2,130)	(1,370)
Net periodic pension/benefit cost (return)	(2,193)	(1,734)	(6,335)	(4,938)
Impact of PUC D&Os	2,052	1,536	5,827	4,385
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	$ (141)	$ (198)	$ (508)	$ (553)