Electric utility segment Additional Information (Details)					1 Months Ended						3 Months Ended			12 Months Ended
	Dec. 30, 2014	Jun. 30, 2014	Jul. 11, 2013 MW	May. 31, 2013 USD ($)	Nov. 30, 2013 USD ($)	Feb. 28, 2013 bid	May. 31, 2012 MW	Mar. 31, 2012 USD ($)	Feb. 28, 2012 USD ($)	Dec. 31, 2009	Nov. 30, 2013 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2014 USD ($) agreement MW	Dec. 31, 2013 USD ($) MW	Dec. 31, 2012 USD ($)	Jul. 31, 2014 USD ($)	Feb. 07, 2014	Feb. 16, 2012 generation_unit
Power purchase agreements
Number of power purchase agreements (PPAs) | agreement														7
Hawaiian Electric Company, Inc (HECO)
Power purchase agreements
Number of power purchase agreements (PPAs) | agreement														7
Purchased power														$ 537,821,000	$ 527,839,000	$ 540,802,000
Renewable projects
Number of Generating Units Subject to New Regulation | generation_unit																			14
D&O
Revenues														2,142,245,000	2,124,174,000	2,228,233,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreements
Purchased power														123,226,000	128,368,000	145,386,000
D&O
Revenues														422,200,000	431,517,000	441,013,000
Maui Electric Company, Limited (MECO)
Power purchase agreements
Purchased power														60,961,000	54,474,000	38,052,000
Environmental regulation
Additional accrued investigation and estimated cleanup costs								$ 3,100,000						3,600,000
D&O
Revenues				$ 5,300,000										422,965,000	424,603,000	440,270,000
Reductions in D&O
Lower ROACE															4,000,000
Customer Information System expenses															300,000
Pension and OPEB expense based on 3-year average															1,500,000
Integrated resource planning expenses															900,000
Operational and Renewable Energy Integration study costs															1,100,000
Total adjustment														$ 7,800,000	7,800,000
Stipulated return on common equity percentage														10.00%
Return on common equity percentage approved by PUC														9.00%
Return on common equity percentage approved by PUC allocated to lower interest rate														0.50%
Return on common equity percentage approved by PUC allocated for OverCurtailment of renewable energy														0.50%
Period as basis for calculation of average pension cost														3 years
Charge recorded net of revenue taxes												$ 7,600,000
Amount to be refunded to customers											$ 9,700,000
Increase (decrease) in employee benefit expenses												(1,800,000)
Deferred IRP cost allowed by PUC order, reclassified to deferred accounts												$ 700,000
General Rate Case Cycle Period	3 years
Estimated increase in revenue, if base rate increased														$ 11,600,000
Estimated increase in revenue, if base rate increased, percentage														2.80%
Estimated cost of common equity, percentage														10.75%
Hawaiian Electric Company, Inc. and Subsidiaries
Fuel contracts
Estimated cost of minimum purchase within 2015 year														$ 400,000,000
Estimated cost of minimum purchase in 2016 year														300,000,000
Estimated cost of minimum purchase in 2017 year														6,400,000
Cost of purchases														$ 1,100,000,000	1,100,000,000	1,300,000,000
Power purchase agreements
Power purchase capacity excluding agreements with smaller IPPs (in megawatts) | MW														575
Purchased power														$ 722,008,000	$ 710,681,000	724,240,000
Expected fixed capacity charges per year for 2015 through 2019, minimum														100,000,000
Expected fixed capacity charges from 2019 through 2033														500,000,000
Renewable projects
Percentage of renewable portfolio standard to be achieved by 2030										40.00%
Recovery of annual deferred costs contingent on approval					$ 405,000
Integration from renewable energy sources (in megawatts) | MW			200												200
Maximum deferred cost recovery									$ 5,890,000
Integration from firm renewable geothermal dispatchable energy (in megawatts) | MW							50
Number of bids received | bid						6
Environmental regulation
Percentage of reduction in GHG emissions by 2020		16.00%
Estimated annual fee, emissions regulation														500,000
D&O
Revenues														2,987,323,000	$ 2,980,172,000	3,109,439,000
Changes in the asset retirement obligation liability
Balance at the beginning of the period														43,106,000	48,431,000
Accretion expense														890,000	1,263,000
Liabilities incurred														0	0
Liabilities settled														(14,577,000)	(5,672,000)
Revisions in estimated cash flows														0	(916,000)
Balance at the end of the period														29,419,000	$ 43,106,000	$ 48,431,000
Decoupling
Public Utilities, baseline capital project value to determine revenue adjustment														$ 2,500,000
Public Utilities, proposed rate base adjustment, percent of previous rate base adjustment																		90.00%
Public Utilites, effective interest rate, revenue balancing account														6.00%
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum
Decoupling
Public Utilities, proposed effective interest rate, revenue balancing account																		1.25%
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum
Decoupling
Public Utilities, proposed effective interest rate, revenue balancing account																		3.25%
East Oahu Transmission Project Phase 1 | Hawaiian Electric Company, Inc. and Subsidiaries
Renewable projects
Gross plant cost agreed to be written-off in lieu of regulatory audit								9,500,000
After-tax charge to net income due to settlement agreement													$ 6,000,000
Additional increase in test year rate case								$ 5,000,000
Reserve for environmental costs
Environmental regulation
Reserve for additional investigation																	$ 800,000