Electric utility segment - Commitments and contingencies (Details)											1 Months Ended								3 Months Ended
	Apr. 27, 2017 USD ($)	Dec. 23, 2016 island	Aug. 11, 2016 USD ($)	Feb. 18, 2016 contract	Jan. 05, 2016 USD ($)	Dec. 22, 2015 USD ($)	Aug. 01, 2015 air_quality_monitoring_station	Oct. 14, 2014 facility	May 31, 2013	Feb. 16, 2012 generation_unit	Oct. 31, 2016 customer	Sep. 30, 2015 USD ($)	Jun. 30, 2015 MW	Aug. 31, 2014	Apr. 30, 2014 order	Aug. 31, 2012 MW	May 31, 2012 MW	Mar. 31, 1988 MW	Mar. 31, 2017 USD ($) agreement contract MW	Mar. 31, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2045	Dec. 31, 2016 USD ($)	Jul. 31, 2014 USD ($)	Jun. 20, 2014	Mar. 01, 2014	Feb. 07, 2014
Regulatory projects and legal obligations
Purchase commitment, period (in years)																		30 years
Minimum power volume required (in megawatts) | MW																186		180
Additional capacity requirement (in megawatts) | MW													9
ERP/EAM Project, expected costs																								$ 82,400,000
SAP software costs																					$ 4,800,000
ERP/EAM cost recovery cap			$ 77,600,000
Public utility, ERP/EAM required pass through savings to customers			$ 244,000,000
ERP/EAM project service period (in years)			12 years
Schofield generating station facility capacity (in megawatts) | MW																50
Schofield generating station project, budgetary cap					$ 157,300,000							$ 167,000,000
Percent of costs recoverable through recovery mechanisms other than base rates (as a percent)												90.00%
Decrease in project costs					$ 9,700,000
Project lease term (in years)					35 years
Number of power plants affected by CWA section 316(b) (in facilities) | facility								3
Environmental regulation
Number of EGUs impacted by proposed rules of MATS (in generation units) | generation_unit										14
Number of additional air quality monitor stations (in air quality monitoring stations) | air_quality_monitoring_station							2
Changes in the asset retirement obligation liability
Accounts receivable and unbilled revenues, net																			$ 252,416,000				$ 237,950,000
Number of orders from regulatory agency (in orders) | order															4
Percent of energy production from renewable energy sources (as a percent)														65.00%
PSIPs, Number of years covered (in years)		5 years
PSIPs, Number of geographic regions covered (in islands) | island		5
Public utilities, duration of Time of Use Program (in years)											2 years
Public utilities, number of customers impacted by Time Of Use Program (in customers) | customer											5,000
Designated as Hedging Instrument | Window forward contract | Cash Flow Hedging
Changes in the asset retirement obligation liability
Notional amount																			15,838,000				20,734,000
Fair Value																			(277,000)				$ (743,000)
Scenario, Forecast
Changes in the asset retirement obligation liability
Expected portfolio standard (as a percent)																						100.00%
Subsequent Event
Changes in the asset retirement obligation liability
Decoupling order, service reliability performance, historical measurement period (in years)	10 years
Maximum penalty as a percent of equity (as a percent)	20.00%
Service reliability, maximum penalty	$ 3,000,000
Call center performance, maximum penalty	$ 1,200,000
Average annual performance, measurement period (in days)	730 days
Dead band percentage above or below the target (as a percent)	3.00%
Maximum incentive, percent of return on equity (as a percent)	8.00%
Period to file proposed tariffs (in days)	30 days
Decoupling order, comment period for proposed tariffs (in days)	60 days
Threshold of capital expenditures in excess of customer contributions for qualification for major project interim recovery	$ 2,500,000
PCB Contamination
Environmental regulation
Valuation allowances and reserves																			$ 5,000,000
Hawaii Electric Light Company, Inc. (HELCO) | Hamakua Energy Partners, L.P. (HEP)
Regulatory projects and legal obligations
Potential purchase price						$ 84,500,000
Hawaii Electric Light Company, Inc. (HELCO) | Maximum
Regulatory projects and legal obligations
Power purchase capacity that Increases from initial capacity (in megawatts) | MW																			60
Hamakua Energy Partners, L.P. (HEP)
Regulatory projects and legal obligations
Percent of island's generating capacity (as a percent)																			23.00%
Hawaiian Electric Company, Inc. and Subsidiaries
Environmental regulation
Percentage of reduction in GHG emissions by 2020 (as a percent)																									16.00%
Estimated annual fee for greenhouse gas emissions																			$ 500,000
Impact on earnings from recognition of AROs																			0
Changes in the asset retirement obligation liability
Balance, beginning of period																			25,589,000	$ 26,848,000
Accretion expense																			3,000	3,000
Liabilities incurred																			0	0
Liabilities settled																			(403,000)	(138,000)
Revisions in estimated cash flows																			0	0
Balance, end of period																			$ 25,189,000	$ 26,713,000
Decoupling implementation experience, period (in years)									3 years
Proposed rate base adjustment, percent of previous rate base adjustment (as a percent)																											90.00%
Effective interest rate, revenue balancing account (as a percent)																											6.00%
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum
Changes in the asset retirement obligation liability
Proposed effective interest rate, revenue balancing account (as a percent)																										3.25%
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum
Changes in the asset retirement obligation liability
Proposed effective interest rate, revenue balancing account (as a percent)																										1.25%
Hawaiian Electric Company
Regulatory projects and legal obligations
Number of power purchase agreements (PPAs) (in agreements) | agreement																			5
Environmental regulation
Period of extension resulting in MATS compliance date (in years)										1 year
Maui Electric
Environmental regulation
Additional accrued investigation and estimated cleanup costs																			$ 3,600,000
Biodiesel Fuel
Regulatory projects and legal obligations
Number of power purchase agreements (PPAs) (in agreements) | contract																			3
Chevron
Regulatory projects and legal obligations
Number of power purchase agreements (PPAs) (in agreements) | contract				2
Pacific Biodiesel Technologies, LLC | Biodiesel Fuel
Regulatory projects and legal obligations
Number of power purchase agreements (PPAs) (in agreements) | contract																			2
PPA extension period (in years)																			1 year
REG Marketing & Logistics, LLC | Biodiesel Fuel
Regulatory projects and legal obligations
Number of power purchase agreements (PPAs) (in agreements) | contract																			1
PPA extension period (in years)																			1 year
Hu Honua Bioenergy, LLC
Regulatory projects and legal obligations
Minimum power volume required (in megawatts) | MW																	21.5
Hawaiian Telcom
Changes in the asset retirement obligation liability
Accounts receivable and unbilled revenues, net																			$ 21,700,000
Reserve for interest accrued																			4,500,000
Hawaiian Telcom | Hawaii Electric Light Company, Inc. (HELCO)
Changes in the asset retirement obligation liability
Accounts receivable and unbilled revenues, net																			5,900,000
Hawaiian Telcom | Hawaiian Electric Company
Changes in the asset retirement obligation liability
Accounts receivable and unbilled revenues, net																			14,500,000
Hawaiian Telcom | Maui Electric
Changes in the asset retirement obligation liability
Accounts receivable and unbilled revenues, net																			$ 1,300,000