Retirement benefits (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Defined benefit plans
Expected payments for remainder of fiscal year	$ 2,000,000		$ 2,000,000
Payments for benefits					$ 2,000,000
Retirement benefits expense			$ 27,000,000	$ 24,000,000
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case			5 years
Defined contribution plan, expenses recognized			$ 4,000,000	3,400,000
Cash contributions by the employer to defined contribution plan			4,300,000	4,200,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			66,000,000	45,000,000
Service cost	16,577,000	$ 12,306,000	49,683,000	36,958,000
Interest cost	19,229,000	18,044,000	57,731,000	54,158,000
Expected return on plan assets	(22,126,000)	(20,337,000)	(66,426,000)	(61,018,000)
Amortization of net prior service loss (gain)	1,000	22,000	3,000	66,000
Amortization of net actuarial loss (gain)	9,191,000	5,064,000	27,608,000	15,240,000
Net periodic benefit cost (credit)	22,872,000	15,099,000	68,599,000	45,404,000
Impact of PUC D&Os	(10,017,000)	(3,331,000)	(29,994,000)	(9,993,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	12,855,000	11,768,000	38,605,000	35,411,000
Other benefits
Defined benefit plans
Contributions expected to be paid in current year			88,000,000		60,000,000
Service cost	982,000	870,000	2,945,000	2,619,000
Interest cost	2,254,000	2,137,000	6,757,000	6,414,000
Expected return on plan assets	(2,912,000)	(2,724,000)	(8,753,000)	(8,180,000)
Amortization of net prior service loss (gain)	(448,000)	(448,000)	(1,345,000)	(1,345,000)
Amortization of net actuarial loss (gain)	450,000	(2,000)	1,346,000	(8,000)
Net periodic benefit cost (credit)	326,000	(167,000)	950,000	(500,000)
Impact of PUC D&Os	(60,000)	494,000	(180,000)	1,482,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	266,000	327,000	770,000	982,000
American Savings Bank (ASB) | Other benefits
Defined benefit plans
Contributions expected to be paid in current year			0		0
HECO Consolidated
Defined benefit plans
Expected payments for remainder of fiscal year	1,000,000		1,000,000
Payments for benefits					1,000,000
Retirement benefits expense			22,000,000	23,000,000
Defined contribution plan, expenses recognized			1,100,000	700,000
Cash contributions by the employer to defined contribution plan			1,100,000	700,000
HECO Consolidated | Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			65,000,000	44,000,000
Service cost	16,066,000	11,900,000	48,197,000	35,698,000
Interest cost	17,632,000	16,495,000	52,897,000	49,484,000
Expected return on plan assets	(20,635,000)	(18,167,000)	(61,906,000)	(54,496,000)
Amortization of net prior service loss (gain)	10,000	15,000	30,000	46,000
Amortization of net actuarial loss (gain)	8,342,000	4,616,000	25,028,000	13,845,000
Net periodic benefit cost (credit)	21,415,000	14,859,000	64,246,000	44,577,000
Impact of PUC D&Os	(10,017,000)	(3,331,000)	(29,994,000)	(9,993,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,398,000	11,528,000	34,252,000	34,584,000
HECO Consolidated | Other benefits
Defined benefit plans
Contributions expected to be paid in current year			86,000,000		59,000,000
Service cost	967,000	848,000	2,902,000	2,544,000
Interest cost	2,175,000	2,058,000	6,525,000	6,175,000
Expected return on plan assets	(2,873,000)	(2,684,000)	(8,621,000)	(8,054,000)
Amortization of net prior service loss (gain)	(450,000)	(451,000)	(1,352,000)	(1,353,000)
Amortization of net actuarial loss (gain)	438,000	0	1,315,000	0
Net periodic benefit cost (credit)	257,000	(229,000)	769,000	(688,000)
Impact of PUC D&Os	(60,000)	494,000	(180,000)	1,482,000
Net periodic benefit cost (adjusted for impact of PUC D&Os)	$ 197,000	$ 265,000	589,000	$ 794,000
Hawaiian Electric Industries, Inc. | Other benefits
Defined benefit plans
Contributions expected to be paid in current year			$ 2,000,000		$ 1,000,000