Retirement benefits - Schedule of Components of Net Periodic Benefit Cost for Consolidated HEI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Pension benefits
Defined Benefit Plan
Service cost	$ 9,838	$ 9,948
Interest cost	27,564	26,305
Expected return on plan assets	(33,832)	(33,857)
Amortization of net actuarial (gain)/losses	66	65
Net periodic pension/benefit cost (return)	3,636	2,461
Impact of PUC D&Os	16,617	17,799
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	20,253	20,260
Other benefits
Defined Benefit Plan
Service cost	246	248
Interest cost	1,779	1,821
Expected return on plan assets	(3,592)	(3,510)
Amortization of net actuarial (gain)/losses	(682)	(746)
Net periodic pension/benefit cost (return)	(2,249)	(2,187)
Impact of PUC D&Os	2,084	2,025
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	(165)	(162)
Hawaiian Electric Company, Inc. and Subsidiaries | Pension benefits
Defined Benefit Plan
Service cost	9,650	9,705
Interest cost	26,666	25,429
Expected return on plan assets	(33,038)	(33,049)
Amortization of net actuarial (gain)/losses	25	23
Net periodic pension/benefit cost (return)	3,303	2,108
Impact of PUC D&Os	16,617	17,799
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	19,920	19,907
Hawaiian Electric Company, Inc. and Subsidiaries | Other benefits
Defined Benefit Plan
Service cost	243	245
Interest cost	1,699	1,741
Expected return on plan assets	(3,545)	(3,462)
Amortization of net actuarial (gain)/losses	(675)	(737)
Net periodic pension/benefit cost (return)	(2,278)	(2,213)
Impact of PUC D&Os	2,084	2,025
Net periodic pension/benefit cost (return) (adjusted for impact of PUC D&Os)	$ (194)	$ (188)