Retirement benefits - Components of NPPC and NPBC (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Pension benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 45,821	$ 45,228	$ 77,823
Interest cost	101,882	98,606	76,817
Expected return on plan assets	(138,422)	(135,189)	(137,160)
Amortization of net prior service gain	0	0	0
Amortization of net actuarial losses (gains)	359	182	27,285
Net periodic pension/benefit cost	9,640	8,827	44,765
Impact of PUC D&Os	71,448	71,905	37,148
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	81,088	80,732	81,913
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	44,669	44,143	75,845
Interest cost	98,492	95,351	74,363
Expected return on plan assets	(135,095)	(131,962)	(133,873)
Amortization of net prior service gain	0	0	0
Amortization of net actuarial losses (gains)	99	28	26,358
Net periodic pension/benefit cost	8,165	7,560	42,693
Impact of PUC D&Os	71,448	71,905	37,148
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	79,613	79,465	79,841
Other benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,112	1,430	2,580
Interest cost	7,365	8,497	6,488
Expected return on plan assets	(13,950)	(13,648)	(13,621)
Amortization of net prior service gain	0	(875)	(928)
Amortization of net actuarial losses (gains)	(2,898)	(1,865)	(8)
Net periodic pension/benefit cost	(8,371)	(6,461)	(5,489)
Impact of PUC D&Os	7,769	5,846	4,966
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(602)	(615)	(523)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	1,096	1,415	2,554
Interest cost	7,039	8,143	6,227
Expected return on plan assets	(13,742)	(13,442)	(13,381)
Amortization of net prior service gain	0	(872)	(925)
Amortization of net actuarial losses (gains)	(2,840)	(1,827)	0
Net periodic pension/benefit cost	(8,447)	(6,583)	(5,525)
Impact of PUC D&Os	7,769	5,846	4,966
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (678)	$ (737)	$ (559)