Retirement benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Defined Benefit Plan
Contributions made to defined benefit plans	$ 10,000	$ 9,000
Contributions expected to be paid in current year	41,000		$ 52,000
Expected payments for remainder of fiscal year	3,000		1,000
Retirement benefits expense	$ 12,000	11,000
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	$ 2,000	1,700
Cash contributions by the employer to defined contribution plan	$ 1,900	1,800
Employer contribution, percent of employee annual compensation	10.00%
Pension benefits
Defined Benefit Plan
Service cost	$ 19,824	20,464
Interest cost	19,811	18,801
Expected return on plan assets	(35,333)	(33,067)
Amortization of net prior period gain	0	0
Amortization of net actuarial (gain) losses	6,297	1,556
Net periodic pension/benefit cost (return)	10,599	7,754
Impact of PUC D&Os	9,551	11,167
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	20,150	18,921
Other benefits
Defined Benefit Plan
Service cost	656	705
Interest cost	1,637	1,569
Expected return on plan assets	(3,397)	(3,233)
Amortization of net prior period gain	(232)	(383)
Amortization of net actuarial (gain) losses	(3)	254
Net periodic pension/benefit cost (return)	(1,339)	(1,088)
Impact of PUC D&Os	1,219	970
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(120)	(118)
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Contributions made to defined benefit plans	10,000	9,000
Contributions expected to be paid in current year	41,000		51,000
Expected payments for remainder of fiscal year	1,000		$ 1,000
Retirement benefits expense	12,000	12,000
Defined contribution plan, expenses recognized	900	800
Cash contributions by the employer to defined contribution plan	900	800
Hawaiian Electric Company, Inc. and Subsidiaries | Pension benefits
Defined Benefit Plan
Service cost	19,318	19,994
Interest cost	18,462	17,531
Expected return on plan assets	(33,546)	(31,368)
Amortization of net prior period gain	0	0
Amortization of net actuarial (gain) losses	6,125	2,559
Net periodic pension/benefit cost (return)	10,359	8,716
Impact of PUC D&Os	9,551	11,167
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	19,910	19,883
Hawaiian Electric Company, Inc. and Subsidiaries | Other benefits
Defined Benefit Plan
Service cost	649	699
Interest cost	1,573	1,504
Expected return on plan assets	(3,347)	(3,182)
Amortization of net prior period gain	(231)	(383)
Amortization of net actuarial (gain) losses	0	250
Net periodic pension/benefit cost (return)	(1,356)	(1,112)
Impact of PUC D&Os	1,219	970
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (137)	$ (142)