Retirement benefits (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Defined Benefit Plan
Expected payments for remainder of fiscal year	$ 3,000		$ 3,000		$ 2,000
Retirement benefits expense			$ 31,000	$ 29,000
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			$ 3,700	3,600
Cash contributions by the employer to defined contribution plan			4,600	4,900
Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Expected payments for remainder of fiscal year	1,000		1,000		1,000
Retirement benefits expense			29,000	29,000
Defined contribution plan, expenses recognized			1,400	1,300
Cash contributions by the employer to defined contribution plan			1,400	1,300
Pension benefits
Defined Benefit Plan
Contributions made to defined benefit plans			17,000	24,000
Contributions expected to be paid in current year	71,000		71,000		49,000
Service cost	18,362	$ 15,382	36,725	30,764
Interest cost	20,164	21,033	40,327	42,066
Expected return on plan assets	(28,465)	(27,999)	(56,931)	(55,997)
Amortization of net prior period (gain)/cost	2	(11)	5	(22)
Amortization of net actuarial (gains)/losses	8,058	3,839	16,115	7,678
Net periodic pension/benefit cost (return)	18,121	12,244	36,241	24,489
Impact of PUC D&Os	6,261	12,278	12,523	24,557
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	24,382	24,522	48,764	49,046
Pension benefits | American Savings Bank (ASB)
Defined Benefit Plan
Contributions expected to be paid in current year	0		0		0
Pension benefits | Hawaiian Electric Industries, Inc.
Defined Benefit Plan
Contributions expected to be paid in current year	1,000		1,000		1,000
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Contributions made to defined benefit plans			17,000	23,000
Contributions expected to be paid in current year	70,000		70,000		$ 48,000
Service cost	17,891	15,001	35,782	30,002
Interest cost	18,715	19,414	37,430	38,828
Expected return on plan assets	(26,857)	(26,164)	(53,712)	(52,328)
Amortization of net prior period (gain)/cost	3	2	5	4
Amortization of net actuarial (gains)/losses	7,369	3,576	14,737	7,152
Net periodic pension/benefit cost (return)	17,121	11,829	34,242	23,658
Impact of PUC D&Os	6,261	12,278	12,523	24,557
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	23,382	24,107	46,765	48,215
Other benefits
Defined Benefit Plan
Service cost	631	542	1,262	1,083
Interest cost	1,856	1,997	3,711	3,994
Expected return on plan assets	(3,039)	(3,086)	(6,077)	(6,172)
Amortization of net prior period (gain)/cost	(441)	(452)	(881)	(904)
Amortization of net actuarial (gains)/losses	51	(4)	101	(7)
Net periodic pension/benefit cost (return)	(942)	(1,003)	(1,884)	(2,006)
Impact of PUC D&Os	777	811	1,554	1,622
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	(165)	(192)	(330)	(384)
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries
Defined Benefit Plan
Service cost	625	538	1,251	1,075
Interest cost	1,781	1,918	3,563	3,835
Expected return on plan assets	(2,990)	(3,036)	(5,980)	(6,071)
Amortization of net prior period (gain)/cost	(439)	(451)	(879)	(902)
Amortization of net actuarial (gains)/losses	51	0	102	0
Net periodic pension/benefit cost (return)	(972)	(1,031)	(1,943)	(2,063)
Impact of PUC D&Os	777	811	1,554	1,622
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ (195)	$ (220)	$ (389)	$ (441)