Retirement benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Defined Benefit Plan
Contributions made to defined benefit plans			$ 23,000	$ 17,000
Contributions expected to be paid in current year	$ 52,000		52,000		$ 71,000
Expected payments for remainder of fiscal year	3,000		3,000		2,000
Retirement benefits expense			$ 23,000	31,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case (in years)			5 years
Defined contribution plan, expenses recognized			$ 3,200	3,700
Cash contributions by the employer to defined contribution plan			3,200	4,600
American Savings Bank (ASB)
Defined Benefit Plan
Contributions expected to be paid in current year	0		0		0
Hawaiian Electric Industries, Inc.
Defined Benefit Plan
Contributions expected to be paid in current year	1,000		1,000		1,000
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Contributions made to defined benefit plans			23,000	17,000
Contributions expected to be paid in current year	51,000		51,000		70,000
Expected payments for remainder of fiscal year	1,000		1,000		$ 1,000
Retirement benefits expense			23,000	29,000
Defined contribution plan, expenses recognized			1,500	1,400
Cash contributions by the employer to defined contribution plan			1,500	1,400
Pension benefits
Defined Benefit Plan
Service cost	20,465	$ 18,362	40,929	36,725
Interest cost	18,800	20,164	37,601	40,327
Expected return on plan assets	(33,068)	(28,465)	(66,135)	(56,931)
Amortization of net prior period (gain)/cost	0	2	0	5
Amortization of net actuarial losses	8,431	8,058	9,987	16,115
Net periodic pension/benefit cost (return)	14,628	18,121	22,382	36,241
Impact of PUC D&Os	5,513	6,261	16,680	12,523
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	20,141	24,382	39,062	48,764
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Service cost	19,993	17,891	39,987	35,782
Interest cost	17,531	18,715	35,062	37,430
Expected return on plan assets	(31,367)	(26,857)	(62,735)	(53,712)
Amortization of net prior period (gain)/cost	0	3	0	5
Amortization of net actuarial losses	8,212	7,369	10,771	14,737
Net periodic pension/benefit cost (return)	14,369	17,121	23,085	34,242
Impact of PUC D&Os	5,513	6,261	16,680	12,523
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	19,882	23,382	39,765	46,765
Other benefits
Defined Benefit Plan
Service cost	705	631	1,410	1,262
Interest cost	1,569	1,856	3,138	3,711
Expected return on plan assets	(3,232)	(3,039)	(6,465)	(6,077)
Amortization of net prior period (gain)/cost	(384)	(441)	(767)	(881)
Amortization of net actuarial losses	44	51	298	101
Net periodic pension/benefit cost (return)	(1,298)	(942)	(2,386)	(1,884)
Impact of PUC D&Os	1,176	777	2,146	1,554
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(122)	(165)	(240)	(330)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Service cost	698	625	1,397	1,251
Interest cost	1,504	1,781	3,008	3,563
Expected return on plan assets	(3,182)	(2,990)	(6,364)	(5,980)
Amortization of net prior period (gain)/cost	(382)	(439)	(765)	(879)
Amortization of net actuarial losses	43	51	293	102
Net periodic pension/benefit cost (return)	(1,319)	(972)	(2,431)	(1,943)
Impact of PUC D&Os	1,176	777	2,146	1,554
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (143)	$ (195)	$ (285)	$ (389)