Electric utility segment - Additional Information (Details)												1 Months Ended											3 Months Ended	12 Months Ended
	Aug. 25, 2016 USD ($)	Aug. 11, 2016 USD ($)	May 19, 2016 USD ($)	Apr. 18, 2016 USD ($)	Feb. 18, 2016 contract	Jan. 05, 2016 USD ($)	Dec. 22, 2015 USD ($)	Oct. 30, 2015 USD ($)	Jun. 30, 2014	May 31, 2013	Feb. 16, 2012 generation_unit	Nov. 30, 2015 USD ($)	Oct. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 MW	Oct. 31, 2014 bidder	Aug. 31, 2014	Jul. 31, 2014 USD ($)	Feb. 28, 2013 bid	Aug. 31, 2012 MW	May 31, 2012 MW	Mar. 31, 1988 MW	Sep. 30, 2015 USD ($)	Dec. 31, 2016 USD ($) agreement contract MW	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2045	Jul. 19, 2016 USD ($)	Jun. 20, 2014	Feb. 07, 2014
Power purchase agreements
Number of power purchase agreements (PPAs) | agreement																								5
PUC request to convert to natural gas, cost																												$ 341,000,000
PUC request for containers, cost																												117,000,000
PUC request, construction of generation system at power plant, cost																												$ 859,000,000
Renewable projects
ERP/EAM Implementation project cost																		$ 82,400,000
Software acquisition cost																							$ 4,800,000
ERP/EAM cost recovery cap		$ 77,600,000
ERP/EAM required pass-through savings		$ 244,000,000
ERP/EAM project service period (in years)		12 years
Project facility capacity (in mW) | MW																				50
Maximum project budget						$ 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
Project, lease term (in years)						35 years
Decoupling
Revenue requirement for plant additions				$ 35,700,000									$ 40,300,000
Power supply improvement plan, percent of energy produced from renewable sources																	65.00%
Derivative financial instrument
Derivative, maturity window						30 days
Accounts receivable and unbilled revenues, net																								$ 237,950,000	$ 242,766,000
Cash Flow Hedging | Foreign Exchange Forward | Designated as Hedging Instrument
Derivative financial instrument
Notional amount																								20,734,000
Fair value																								(743,000)
Scenario, Forecast
Decoupling
Percentage of expected renewable portfolio standard																											100.00%
PCB Contamination
Environmental regulation
Accrual for environmental loss contingencies																								$ 4,100,000
Biodiesel Fuel
Power purchase agreements
Number of power purchase agreements (PPAs) | contract																								3
Chevron
Power purchase agreements
Number of power purchase agreements (PPAs) | contract					2
Pacific Biodiesel Technologies | Biodiesel Fuel
Power purchase agreements
Number of power purchase agreements (PPAs) | contract																								2
Power purchase agreement, extension period (in years)																								1 year
REG Marketing & Logistics | Biodiesel Fuel
Power purchase agreements
Number of power purchase agreements (PPAs) | contract																								1
Power purchase agreement, extension period (in years)																								1 year
Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreements
Period following written notification of contract negotiation termination (in days)																								60 days
AES Hawaii, Inc. (AES Hawaii)
Power purchase agreements
Purchase commitment, period																						30 years
Purchase commitment, minimum power volume required to be purchased | MW																				186		180
Purchase commitment, arbitration, additional capacity requirement | MW															9
Hu Honua Bioenergy
Power purchase agreements
Purchase commitment, minimum power volume required to be purchased | MW																					21.5
Hawaiian Telcom
Derivative financial instrument
Accounts receivable and unbilled revenues, net																								$ 21,300,000
Hawaiian Electric Company, Inc (HECO)
Power purchase agreements
Number of power purchase agreements (PPAs) | agreement																								5
Purchased power																								$ 431,009,000	440,983,000	$ 537,821,000
Environmental regulation
Number of generating units subject to new regulation | generation_unit											14
Extension period resulting in mercury and air toxics standards compliance date											1 year
Decoupling
Annual incremental RAM adjusted revenues			$ 11,000,000
Hawaiian Electric Company, Inc (HECO) | Hawaiian Telcom
Derivative financial instrument
Accounts receivable and unbilled revenues, net																								14,200,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreements
Purchased power																								81,018,000	97,503,000	123,226,000
Maui Electric Company, Limited (MECO)
Power purchase agreements
Purchased power																								50,713,000	55,610,000	60,961,000
Environmental regulation
Additional accrued investigation and estimated cleanup costs																								3,600,000
Hawaiian Electric Company, Inc. and Subsidiaries
Fuel contracts
Estimated cost of minimum purchase within 2015 year																								125,000,000
Estimated cost of minimum purchase in 2016 year																								119,000,000
Estimated cost of minimum purchase in 2017 year																								119,000,000
Cost of purchases																								$ 400,000,000	600,000,000	1,100,000,000
Power purchase agreements
Power purchase capacity excluding agreements with smaller IPPs (in megawatts) | MW																								551
Purchased power																								$ 562,740,000	594,096,000	722,008,000
Expected fixed capacity charges per year for 2015 through 2019, minimum																								100,000,000
Expected fixed capacity charges from 2019 through 2033																								400,000,000
Renewable projects
Integration from firm renewable geothermal dispatchable energy (in megawatts) | MW																					50
Maximum deferred cost recovery - geothermal dispatchable energy costs												$ 2,100,000
Number of bids received | bid																			6
Number of eligible bidders | bidder																5
Environmental regulation
Percent of reduction in GHG emissions mandated by regulations																													16.00%
Percentage of reduction in GHG emissions by 2020									16.00%
Estimated annual fee, emissions regulation																								500,000
ARO, recognition impact on earnings																								0
Changes in the asset retirement obligation liability
Balance at the beginning of the period																								26,848,000	29,419,000
Accretion expense																								10,000	24,000
Liabilities incurred																								0	0
Liabilities settled																								(1,269,000)	(2,595,000)
Revisions in estimated cash flows																								0	0
Balance at the end of the period																								25,589,000	$ 26,848,000	$ 29,419,000
Decoupling
Reduction in pro forma net earnings																								$ 14,000,000
Decoupling implementation experience (in years)										3 years
Public Utilities, proposed rate base adjustment, percent of previous rate base adjustment																														90.00%
Public Utilities, 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%
HELCO
Decoupling
Annual incremental RAM adjusted revenues			2,300,000
HELCO | Hamakua Energy Partners, L.P. (HEP)
Renewable projects
Consideration transferred							$ 84,500,000
HELCO | Maximum
Renewable projects
Power purchase capacity (in megawatts) | MW																								60
HELCO | Hawaiian Telcom
Derivative financial instrument
Accounts receivable and unbilled revenues, net																								$ 5,700,000
Hamakua Energy Partners, L.P. (HEP)
Renewable projects
Percent of generating capacity for area																								23.00%
MECO
Decoupling
Revenue requirement for plant additions								$ 4,300,000
Revenue requirement for plant additions, recovery requested	$ 27,200,000
Annual incremental RAM adjusted revenues			$ 2,400,000
MECO | Hawaiian Telcom
Derivative financial instrument
Accounts receivable and unbilled revenues, net																								$ 1,400,000