Electric utility segment - Commitments and contingencies (Details)											1 Months Ended													3 Months Ended		6 Months Ended		22 Months Ended
	May 19, 2016 USD ($) kWh	Apr. 18, 2016 USD ($)	Feb. 18, 2016	Jan. 05, 2016 USD ($)	Nov. 13, 2015 MW	Oct. 30, 2015 USD ($)	Oct. 26, 2015 USD ($)	Aug. 03, 2015 state	May 31, 2013	Feb. 16, 2012 generation_unit	Nov. 30, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($) MW	May 31, 2015 USD ($)	Oct. 31, 2014 bidder	Aug. 31, 2014	Jul. 31, 2014 USD ($)	Apr. 30, 2014 order	Feb. 28, 2013 bid	Aug. 31, 2012 MW	May 31, 2012 MW	Feb. 28, 2012 USD ($)	Mar. 31, 1988 MW	Jun. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2015 USD ($)	Dec. 31, 2013 USD ($) MW	Dec. 31, 2045	Jul. 19, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 20, 2014	Mar. 01, 2014	Feb. 07, 2014
Regulatory projects and legal obligations
Fuel supply contract term			3 years
Purchase commitment, period																							30 years
Minimum power volume required | MW					180															186			180
Additional capacity requirement | MW					9								9
Enterprise resource management system project, estimated costs																	$ 82,400,000
Enterprise resource management system project, difference between Option A and B														$ 20,800,000
SAP software costs																									$ 4,800,000
Schofield generating station facility capacity | 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												90.00%
Decrease in project costs				$ 9,700,000
Environmental regulation
Number of EGUs impacted by proposed rules of MATS | generation_unit										14
Environmental remediation expense																										$ 200,000
States included in interim state-wide emission limits | state								48
Public Utilities, Phase-in Plans [Abstract]
Revenue requirement associated with plant additions		$ 35,700,000					$ 40,300,000
Accounts receivable and unbilled revenues, net																								$ 224,179,000		224,179,000					$ 242,766,000
Number of orders from regulatory agency | order																		4
Percent of energy production from renewable energy sources																65.00%
Derivative measurement range				30 days
Designated as Hedging Instrument | Window forward contract | Cash Flow Hedging
Public Utilities, Phase-in Plans [Abstract]
Notional amount																								20,637,000		20,637,000					0
Fair value																								466,000		466,000					$ 0
Scenario, Forecast
Public Utilities, Phase-in Plans [Abstract]
Expected portfolio standard																													100.00%
Hawaiian Telcom
Public Utilities, Phase-in Plans [Abstract]
Accounts receivable and unbilled revenues, net																								19,200,000		19,200,000
Accrued interest receivable																								3,500,000		3,500,000
Expected receivable																								15,700,000		15,700,000
PCB Contamination
Environmental regulation
Valuation allowances and reserves																								4,500,000		4,500,000
US Fish and Wildlife Service
Environmental regulation
Environmental penalty expense																								250
Hawaiian Electric Company, Inc. and Subsidiaries
Regulatory projects and legal obligations
Maximum deferred costs, inter-island projects																						$ 5,890,000
Maximum deferred cost recovery, contractor service costs																												$ 3,100,000
Integration from renewable energy sources (in megawatts) | MW																												200
Maximum deferred cost recovery, contractor service costs, amortization period																												3 years
Capacity integration from dispatchable renewable geothermal sources | MW																					50
Deferred cost recovery of geothermal dispatchable energy costs											$ 2,100,000
Number of bids received | bid																			6
Number of eligible bidders | bidder															5
Environmental regulation
Percentage of reduction in GHG emissions by 2020																																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																									$ 27,550,000	26,848,000	$ 29,419,000
Accretion expense																										7,000	12,000
Liabilities incurred																										0	0
Liabilities settled																										(259,000)	(1,881,000)
Revisions in estimated cash flows																										0	0
Balance, end of period													$ 27,550,000											26,596,000		26,596,000	$ 27,550,000
Decoupling implementation experience, period									3 years
Proposed rate base adjustment, percent of previous rate base adjustment																																		90.00%
Effective interest rate, revenue balancing account																																		6.00%
Public Utilities, Phase-in Plans [Abstract]
Period to file required plan																		120 days
Hawaiian Electric Company, Inc. and Subsidiaries | Minimum
Changes in the asset retirement obligation liability
Proposed effective interest rate, revenue balancing account																																	1.25%
Hawaiian Electric Company, Inc. and Subsidiaries | Maximum
Changes in the asset retirement obligation liability
Proposed effective interest rate, revenue balancing account																																	3.25%
Hawaiian Electric Company
Environmental regulation
Period of extension resulting in MATS compliance date										1 year
Public Utilities, Phase-in Plans [Abstract]
Annual incremental RAM adjusted revenues	$ 11,000,000
Annual change in accrued earnings sharing credits	0
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes)	(13,600,000)
Net annual incremental decrease in amount to be collected under the tariffs	(2,600,000)
Impact on typical residential customer monthly bill	$ 0.01
Monthly utility usage assumption (in kilowatts per hour) | kWh	500
Hawaiian Electric Company | Hawaiian Telcom
Public Utilities, Phase-in Plans [Abstract]
Accounts receivable and unbilled revenues, net																								13,300,000		13,300,000
Hawaii Electric Light Company, Inc. (HELCO)
Public Utilities, Phase-in Plans [Abstract]
Annual incremental RAM adjusted revenues	$ 2,300,000
Annual change in accrued earnings sharing credits	0
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes)	(2,500,000)
Net annual incremental decrease in amount to be collected under the tariffs	(200,000)
Impact on typical residential customer monthly bill	$ 0.13
Monthly utility usage assumption (in kilowatts per hour) | kWh	500
Hawaii Electric Light Company, Inc. (HELCO) | Hawaiian Telcom
Public Utilities, Phase-in Plans [Abstract]
Accounts receivable and unbilled revenues, net																								5,600,000		5,600,000
Maui Electric
Environmental regulation
Additional accrued investigation and estimated cleanup costs																								3,600,000		3,600,000
Public Utilities, Phase-in Plans [Abstract]
Revenue requirement associated with plant additions						$ 4,300,000
Annual incremental RAM adjusted revenues	$ 2,400,000
Annual change in accrued earnings sharing credits	500,000
Annual change in accrued RBA balance as of December 31, 2015 (and associated revenue taxes)	(4,300,000)
Net annual incremental decrease in amount to be collected under the tariffs	(1,400,000)
Impact on typical residential customer monthly bill	(0.95)
Maui Electric | Hawaiian Telcom
Public Utilities, Phase-in Plans [Abstract]
Accounts receivable and unbilled revenues, net																								$ 300,000		$ 300,000
Lanai and Molokai
Public Utilities, Phase-in Plans [Abstract]
Impact on typical residential customer monthly bill	$ (0.76)
Monthly utility usage assumption (in kilowatts per hour) | kWh	400
Subsequent Event
Regulatory projects and legal obligations
Conversion of existing generating units to natural gas, costs																														$ 341,000,000
Liquefied natural gas containers cost																														117,000,000
Construction of generation system at the Kahe power plant																														$ 859,000,000