Retirement benefits (Details) - USD ($)	3 Months Ended	6 Months Ended	12 Months Ended
Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
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			$ 17,000,000	$ 18,000,000
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			$ 3,300,000	2,800,000
Cash contributions by the employer to defined contribution plan			4,000,000	3,700,000
Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			33,000,000	33,000,000
Contributions expected to be paid in current year			67,000,000		65,000,000
Service cost	15,870,000	$ 14,913,000	32,364,000	30,304,000
Interest cost	20,361,000	20,481,000	40,577,000	40,758,000
Expected return on plan assets	(25,646,000)	(24,616,000)	(51,367,000)	(49,280,000)
Amortization of net prior service gain	(13,000)	(14,000)	(27,000)	(28,000)
Amortization of net actuarial loss	6,707,000	6,408,000	13,220,000	12,377,000
Net periodic pension/benefit cost	17,279,000	17,172,000	34,767,000	34,131,000
Impact of PUC D&Os	(4,867,000)	(4,765,000)	(10,023,000)	(8,811,000)
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	12,412,000	12,407,000	24,744,000	25,320,000
Pension benefits \| American Savings Bank (ASB)
Defined benefit plans
Contributions expected to be paid in current year			0		0
Other benefits
Defined benefit plans
Service cost	847,000	832,000	1,687,000	1,668,000
Interest cost	2,315,000	2,363,000	4,726,000	4,837,000
Expected return on plan assets	(3,104,000)	(3,091,000)	(6,170,000)	(6,143,000)
Amortization of net prior service gain	(448,000)	(448,000)	(897,000)	(896,000)
Amortization of net actuarial loss	199,000	116,000	565,000	403,000
Net periodic pension/benefit cost	(191,000)	(228,000)	(89,000)	(131,000)
Impact of PUC D&Os	527,000	483,000	673,000	672,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	336,000	255,000	584,000	541,000
Hawaiian Electric Company, Inc. and Subsidiaries
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			15,000,000	16,000,000
Defined contribution plan, expenses recognized			1,000,000	800,000
Cash contributions by the employer to defined contribution plan			1,000,000	800,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Pension benefits
Defined benefit plans
Contributions made to defined benefit plans			33,000,000	32,000,000
Contributions expected to be paid in current year			66,000,000		64,000,000
Service cost	15,436,000	14,465,000	31,530,000	29,398,000
Interest cost	18,726,000	18,801,000	37,315,000	37,404,000
Expected return on plan assets	(23,935,000)	(22,885,000)	(47,946,000)	(45,817,000)
Amortization of net prior service gain	2,000	3,000	4,000	7,000
Amortization of net actuarial loss	6,190,000	5,885,000	12,196,000	11,346,000
Net periodic pension/benefit cost	16,419,000	16,269,000	33,099,000	32,338,000
Impact of PUC D&Os	(4,867,000)	(4,765,000)	(10,023,000)	(8,811,000)
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	11,552,000	11,504,000	23,076,000	23,527,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Other benefits
Defined benefit plans
Service cost	841,000	820,000	1,676,000	1,642,000
Interest cost	2,231,000	2,280,000	4,558,000	4,669,000
Expected return on plan assets	(3,056,000)	(3,046,000)	(6,073,000)	(6,049,000)
Amortization of net prior service gain	(451,000)	(451,000)	(902,000)	(902,000)
Amortization of net actuarial loss	192,000	113,000	551,000	397,000
Net periodic pension/benefit cost	(243,000)	(284,000)	(190,000)	(243,000)
Impact of PUC D&Os	527,000	483,000	673,000	672,000
Net periodic pension/benefit cost (adjusted for impact of PUC D&Os)	$ 284,000	$ 199,000	483,000	$ 429,000
Hawaiian Electric Industries, Inc. \| Pension benefits
Defined benefit plans
Contributions expected to be paid in current year			$ 1,000,000		$ 1,000,000

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Represents the total amount of net periodic benefit cost adjusted for impact of Public Utilities Commission's decisions and orders.

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Represents the number of years for which regulatory asset/liability for each utilities will be amortized, beginning with the respective utility's next rate case.

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The amount of gains or losses recognized in net periodic benefit cost.

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The amount of the prior service cost or credit recognized in net periodic benefit cost relating to benefit changes attributable to plan participants' prior service pursuant to a plan amendment or a plan initiation.

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The amount of payments made for which participants are entitled under a pension plan, including pension benefits, death benefits, and benefits due on termination of employment. Also includes payments made under a postretirement benefit plan, including prescription drug benefits, health care benefits, life insurance benefits, and legal, educational and advisory services. This item represents a periodic decrease to the plan obligations and a decrease to plan assets.

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Amount of contributions made by the employer to defined benefit plans.

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Amount of benefits from a defined benefit plan expected to be paid in the remainder of the fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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An amount calculated as a basis for determining the extent of delayed recognition of the effects of changes in the fair value of assets. The expected return on plan assets is determined based on the expected long-term rate of return on plan assets and the market-related value of plan assets.

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The increase in a defined benefit pension plan's projected benefit obligation or a defined benefit postretirement plan's accumulated postretirement benefit obligation due to the passage of time.

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The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss), prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments.

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The actuarial present value of benefits attributed by the pension benefit formula to services rendered by employees during the period. The portion of the expected postretirement benefit obligation attributed to employee service during the period. The service cost component is a portion of the benefit obligation and is unaffected by the funded status of the plan.

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The amount of the cost recognized during the period for defined contribution plans.

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The amount of pension and other (such as medical, dental and life insurance) postretirement benefit costs recognized during the period for (1) defined benefit plans (periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain (loss) on assets, prior service cost or credit, transition asset or obligation, and gain (loss) due to settlements or curtailments) and for (2) defined contribution plans (to the extent that a plan's defined contributions to an individual's account are to be made for periods in which that individual renders services, the net cost for a period is the contribution called for in that period; if a plan calls for contributions for periods after an individual retires or terminates, the estimated cost is accrued during the employee's service period).

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