Retirement benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Defined benefit plans
Expected payments for remainder of fiscal year	$ 3,000		$ 2,000
Retirement benefits expense	$ 15,000	$ 15,000
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	$ 1,800	1,900
Cash contributions by the employer to defined contribution plan	3,200	3,700
Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Expected payments for remainder of fiscal year	1,000		1,000
Retirement benefits expense	14,000	14,000
Defined contribution plan, expenses recognized	700	700
Cash contributions by the employer to defined contribution plan	700	700
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans	17,000	8,000
Contributions expected to be paid in current year	69,000		49,000
Service cost	18,363	15,382
Interest cost	20,163	21,033
Expected return on plan assets	(28,466)	(27,998)
Amortization of net prior period (gain)/cost	3	(11)
Amortization of net actuarial (gains)/losses	8,057	3,839
Net periodic pension/benefit cost (return)	18,120	12,245
Impact of PUC D&Os	6,262	12,279
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,382	24,524
Pension benefits | American Savings Bank (ASB)
Defined benefit plans
Contributions expected to be paid in current year	0		0
Pension benefits | Hawaiian Electric Industries, Inc.
Defined benefit plans
Contributions expected to be paid in current year	1,000		1,000
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Contributions made to defined benefit plans	17,000	8,000
Contributions expected to be paid in current year	68,000		$ 48,000
Service cost	17,891	15,001
Interest cost	18,715	19,414
Expected return on plan assets	(26,855)	(26,164)
Amortization of net prior period (gain)/cost	2	2
Amortization of net actuarial (gains)/losses	7,368	3,576
Net periodic pension/benefit cost (return)	17,121	11,829
Impact of PUC D&Os	6,262	12,279
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	23,383	24,108
Other benefits
Defined benefit plans
Service cost	631	541
Interest cost	1,855	1,997
Expected return on plan assets	(3,038)	(3,086)
Amortization of net prior period (gain)/cost	(440)	(452)
Amortization of net actuarial (gains)/losses	50	(3)
Net periodic pension/benefit cost (return)	(942)	(1,003)
Impact of PUC D&Os	777	811
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(165)	(192)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined benefit plans
Service cost	626	537
Interest cost	1,782	1,917
Expected return on plan assets	(2,990)	(3,035)
Amortization of net prior period (gain)/cost	(440)	(451)
Amortization of net actuarial (gains)/losses	51	0
Net periodic pension/benefit cost (return)	(971)	(1,032)
Impact of PUC D&Os	777	811
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (194)	$ (221)