Summary of significant accounting policies (Details 3) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Basic
Distributed earnings (in dollars per share)									$ 1.24	$ 1.24	$ 1.24
Undistributed earnings (loss) (in dollars per share)									0.41	0.39	0.19
Earnings Per Share, basic (in dollars per share)	$ 0.32	$ 0.47	$ 0.41	$ 0.45	$ 0.39	$ 0.49	$ 0.41	$ 0.34	1.65	1.63	1.43
Diluted
Distributed earnings (in dollars per share)									1.24	1.24	1.24
Undistributed earnings (losses) (in dollars per share)									0.40	0.38	0.18
Earnings Per Share, diluted (in dollars per share)	$ 0.32	$ 0.46	$ 0.41	$ 0.45	$ 0.39	$ 0.48	$ 0.41	$ 0.34	$ 1.64	$ 1.62	$ 1.42
Summary of significant accounting policies
Amount reclassified form other assets to plant and equipment	$ 6,399,724				$ 6,057,936				$ 6,399,724	$ 6,057,936
Other assets	541,542				512,627				541,542	512,627
Accounts Receivable
Allowance for customer accounts receivable, accrued unbilled revenues and other accounts receivable	2,000				2,000				2,000	2,000
Goodwill and other intangibles
Goodwill	$ 82,190				82,190				$ 82,190	82,190
Fair value excess over carrying value (percent)	60.00%								60.00%
Hawaiian Electric Company, Inc. and Subsidiaries
Electric utility revenues
Revenue taxes included in revenues and in taxes, other than income taxes expense									$ 267,000	$ 266,000	$ 280,000
Weighted average AFUDC rate (as a percent)									7.70%	7.60%	7.60%
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum
Contributions in aid of construction
Contributions amortized period									30 years
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum
Contributions in aid of construction
Contributions amortized period									55 years
Bank
Loans modified in a troubled debt restructuring
Number of consecutive months of repayment required for loans to be removed from nonaccrual status									6 months
Goodwill and other intangibles
Goodwill	$ 82,190				82,190				$ 82,190	$ 82,190
Stock appreciation rights (SARs) | Common stock
Antidilutive effect of stock appreciation rights (SARs)
Antidilutive effects of SARs shares that were not included in the computation of diluted EPS (in shares)										102	102
Bank
Summary of significant accounting policies
Other assets	304,435				268,063				304,435	$ 268,063
Goodwill and other intangibles
Goodwill	82,190				82,190				82,190	82,190
Antidilutive effect of stock appreciation rights (SARs)
Commitments to fund affordable housing investments	14,800				600				14,800	600
Affordable housing investment, carrying value	$ 32,457				14,543				$ 32,457	14,543
Restatement adjustment
Summary of significant accounting policies
Amount reclassified form other assets to plant and equipment					7,000					7,000
Other assets					$ (7,000)					$ (7,000)