Retirement benefits - Effects of Restatement (Details) (USD $)	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Retirement benefits expense	$ 8,000,000	$ 10,000,000
As previously filed
Retirement benefits expense		11,000,000
Difference
Retirement benefits expense		(1,000,000)
Hawaiian Electric Company, Inc. and Subsidiaries
Retirement benefits expense	8,000,000	9,000,000
Hawaiian Electric Company, Inc. and Subsidiaries \| As previously filed
Retirement benefits expense		10,000,000
Hawaiian Electric Company, Inc. and Subsidiaries \| Difference
Retirement benefits expense		(1,000,000)
Pension benefits
Impact of PUC D&Os	(3,011,000)	(8,866,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,830,000	13,039,000
Pension benefits \| As previously filed
Impact of PUC D&Os		(7,436,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)		14,469,000
Pension benefits \| Difference
Impact of PUC D&Os		(1,430,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)		(1,430,000)
Pension benefits \| Hawaiian Electric Company, Inc. and Subsidiaries
Impact of PUC D&Os	(3,011,000)	(8,866,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)	11,526,000	11,997,000
Pension benefits \| Hawaiian Electric Company, Inc. and Subsidiaries \| As previously filed
Impact of PUC D&Os		(7,436,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)		13,427,000
Pension benefits \| Hawaiian Electric Company, Inc. and Subsidiaries \| Difference
Impact of PUC D&Os		(1,430,000)
Net periodic benefit cost (adjusted for impact of PUC D&Os)		$ (1,430,000)

- 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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