Retirement benefits - Effects of Restatement (Details) (USD $)	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Retirement benefits expense			$ 24,000,000	$ 24,000,000
Hawaiian Electric Company, Inc. and Subsidiaries
Retirement benefits expense			23,000,000	21,000,000
Pension benefits
Impact of PUC D&Os	(3,331,000)	(9,257,000)	(9,993,000)	(28,847,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,768,000	12,429,000	35,411,000	36,464,000
Pension benefits \| Hawaiian Electric Company, Inc. and Subsidiaries
Impact of PUC D&Os	(3,331,000)	(9,257,000)	(9,993,000)	(28,847,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	$ 11,528,000	$ 11,538,000	$ 34,584,000	$ 33,540,000

- Definition

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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