Retirement benefits - Components of NPPC and NPBC (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Pension benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 81,432	$ 73,387	$ 62,135
Interest cost	75,361	81,335	84,267
Expected return on plan assets	(132,223)	(113,800)	(111,989)
Amortization of net prior service (gain) cost	0	8	(42)
Amortization of net actuarial losses	27,245	33,456	15,479
Net periodic pension/benefit cost	51,815	74,386	49,850
Impact of PUC D&Os	27,963	20,997	48,143
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	79,778	95,383	97,993
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	79,463	71,604	60,461
Interest cost	70,235	75,484	77,851
Expected return on plan assets	(125,404)	(107,369)	(104,632)
Amortization of net prior service (gain) cost	0	9	7
Amortization of net actuarial losses	27,534	30,566	14,658
Net periodic pension/benefit cost	51,828	70,294	48,345
Impact of PUC D&Os	27,963	20,997	48,143
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	79,791	91,291	96,488
Other benefits
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,827	2,537	2,209
Interest cost	6,122	7,407	8,004
Expected return on plan assets	(12,957)	(12,124)	(12,356)
Amortization of net prior service (gain) cost	(1,533)	(1,761)	(1,806)
Amortization of net actuarial losses	203	208	(13)
Net periodic pension/benefit cost	(5,338)	(3,733)	(3,962)
Impact of PUC D&Os	4,839	3,179	3,258
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(499)	(554)	(704)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	2,802	2,515	2,191
Interest cost	5,875	7,103	7,673
Expected return on plan assets	(12,755)	(11,957)	(12,180)
Amortization of net prior service (gain) cost	(1,530)	(1,758)	(1,803)
Amortization of net actuarial losses	206	207	0
Net periodic pension/benefit cost	(5,402)	(3,890)	(4,119)
Impact of PUC D&Os	4,839	3,179	3,258
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (563)	$ (711)	$ (861)