Electric utility segment - Commitments and contingencies (Details)													1 Months Ended							3 Months Ended	12 Months Ended	20 Months Ended	21 Months Ended	31 Months Ended
	Mar. 29, 2018 USD ($)	Mar. 05, 2018 USD ($)	Feb. 16, 2018 USD ($)	Jan. 19, 2018 USD ($)	Dec. 15, 2017 USD ($)	Oct. 12, 2017 USD ($)	Aug. 21, 2017 USD ($)	Jul. 11, 2017	Apr. 27, 2017 USD ($)	Aug. 11, 2016 USD ($)	May 23, 2016	Jan. 05, 2016 USD ($)	Jun. 30, 2017 USD ($) $ / kWh	Jul. 31, 2016 MW	Sep. 30, 2015 USD ($)	Jun. 30, 2015 MW	Aug. 31, 2012 MW	May 31, 2012 MW	Mar. 31, 1988 MW	Mar. 31, 2018 USD ($) $ / kWh	Dec. 31, 1988 MW	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 27, 2018 USD ($)	Feb. 26, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 18, 2017 USD ($)
Regulatory Projects and Legal Obligations [Line Items]
Revenues with respect to interim orders related to general rate increase requests																				$ 7,000,000
Power purchase agreement, termination period											60 days
ERP/EAM cost recovery cap										$ 77,600,000
Public utility, ERP/EAM required pass through savings to customers										$ 244,000,000																		$ 244,000,000
ERP/EAM project service period (in years)										12 years
AFUDC rate										1.75%
ERP/EAM implementation project costs																						$ 47,700,000
ERP/EAM implementation project, operations and management																						8,600,000
ERP/EAM implementation project, capital costs																						2,600,000
ERP/EAM implementation project, deferred costs																						36,500,000
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															90.00%
Decrease in project costs												$ 9,700,000
Project lease term (in years)												35 years
Project cost incurred																								$ 131,600,000
West Lock PV Project, energy generated (in megawatts) | MW														20
West Lock PV Project, cost cap													$ 67,000,000
West Lock PV Project, maximum energy cost (in dollars per kilowatt hours) | $ / kWh													0.0956
West Lock PV Project, project costs incurred																							$ 7,000,000
Accounts receivable and unbilled revenues, net																				$ 266,336,000		266,336,000	266,336,000	266,336,000			$ 263,209,000
Environmental regulation
Threshold of capital expenditures in excess of customer contributions for qualification for major project interim recovery									$ 2,500,000.0
Decoupling order, service reliability performance, historical measurement period (in years)																				10 years
Maximum penalty as a percent of equity																				20.00%
Service reliability, maximum penalty																				$ 6,200,000
Dead band percentage above or below the target																				3.00%
Call center performance, maximum penalty, percent																				8.00%
Call center performance, maximum penalty																				$ 1,200,000
Demand response, award percentage of annual maintenance costs																				5.00%
Demand response, maximum award																				$ 500,000
Demand response, penalty																				$ 0
Expected savings, percent																				20.00%
Energy price, renewable projects with storage capacity (in dollars per kilowatt hour) | $ / kWh																				0.115
Energy price, energy-only renewable projects (in dollars per kilowatt hour) | $ / kWh																				0.095
Performance incentive mechanism, incentive cap																				$ 3,500,000
Performance incentive mechanism penalty																				0
Revenue calculation assumptions, rate of return				7.57%	7.57%
Revenue calculation assumptions, percentage of return on average common equity		9.50%		9.50%	9.50%
General rate increase, revenue, calculation assumptions, rate of return, common equity capitalization percentage				57.00%	57.00%
Interim D&O, reduction in revenue requirement, baseline plant additions					$ 5,000,000
Interim D&O, Reduction in revenue requirement of pension regulatory asset					$ 6,000,000
Statement of probable entitlement, interim increase			$ 36,000,000	$ 36,000,000
Remaining settlement, reduction in revenue requirement		$ 38,300,000
Remaining settlement, reduction in O&M expenses		5,000,000
Remaining settlement, hold-back amount		$ 5,000,000
PCB Contamination
Environmental regulation
Valuation allowances and reserves																				4,700,000		4,700,000	4,700,000	4,700,000
AES Hawaii
Regulatory Projects and Legal Obligations [Line Items]
Purchase commitment, period (in years)																			30 years
Minimum power volume required (in megawatts) | MW																	186		180
Additional capacity requirement (in megawatts) | MW																9
Hu Honua Bioenergy, LLC
Regulatory Projects and Legal Obligations [Line Items]
Minimum power volume required (in megawatts) | MW																		21.5
Hawaiian Telcom
Regulatory Projects and Legal Obligations [Line Items]
Accounts receivable and unbilled revenues, net																				22,400,000		22,400,000	22,400,000	22,400,000
Hawaiian Electric Company
Environmental regulation
Decoupling filing, change in income taxes	$ 0
Hawaiian Electric Company | Hawaiian Telcom
Regulatory Projects and Legal Obligations [Line Items]
Accounts receivable and unbilled revenues, net																				15,100,000		15,100,000	15,100,000	15,100,000
Hawaiian Telcom
Regulatory Projects and Legal Obligations [Line Items]
Accounts receivable and unbilled revenues, net																				48,000,000		48,000,000	48,000,000	48,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Environmental regulation
Decoupling filing, change in income taxes	0
Stipulated ROACE rate							9.50%	9.75%
General rate increase, ROACE, percentage decrease								25.00%
Interim general rate increase granted							$ 9,900,000
Decrease in test year revenue requirement, tax act																									$ 9,500,000
Hawaii Electric Light Company, Inc. (HELCO) | Hawaiian Telcom
Regulatory Projects and Legal Obligations [Line Items]
Accounts receivable and unbilled revenues, net																				6,000,000		6,000,000	6,000,000	6,000,000
Maui Electric
Environmental regulation
Additional accrued investigation and estimated cleanup costs																				2,700,000		2,700,000	2,700,000	2,700,000
Decoupling filing, change in income taxes	$ 2,400,000
General rate increase, revenue, calculation assumptions, rate of return, common equity capitalization percentage						56.90%
General rate increase, revenue						$ 30,100,000
General rate increase, revenue, percent						9.30%
General rate increase, revenue, calculation assumptions, rate of return						8.05%
General rate increase, revenue, calculation assumptions, rate of return, ROACE						10.60%
General rate increase, revenue, calculation assumptions, rate base						$ 473,000,000
Conditional general rate increase, revenue						$ 46,600,000
Conditional general rate increase, revenue, percentage						14.30%
Rate case, income tax expense reduction																										$ 8,100,000
Rate case, annual amortization credit																										500,000
Rate case, increase in rate base resulting from decrease in accumulated deferred income tax																										$ 7,100,000
Maui Electric | Hawaiian Telcom
Regulatory Projects and Legal Obligations [Line Items]
Accounts receivable and unbilled revenues, net																				$ 1,300,000		$ 1,300,000	$ 1,300,000	$ 1,300,000
Kalaeloa Partners, L.P. (Kalaeloa) | Hawaiian Electric Company
Regulatory Projects and Legal Obligations [Line Items]
Increased power purchase commitment capacity (in megawatts) | MW																					208