Electric utility segment - Unconsolidated variable interest entities (Details)	1 Months Ended				3 Months Ended		9 Months Ended
	Oct. 31, 2015 MW	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	Oct. 31, 1988 MW	Sep. 30, 2015 USD ($) entity	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) agreement entity kW	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Power purchase agreement
Purchases from IPPs					$ 161,000,000	$ 193,000,000	$ 446,000,000	$ 546,000,000
Termination period							60 days
Accounts payable					$ 152,896,000		$ 152,896,000		$ 186,425,000
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) | agreement							6
Maximum capacity of small power production facilities (in kilowatts) | kW							100
Number of entities currently not required to be consolidated as VIEs | entity					0		0
Purchases from IPPs					$ 119,302,000	142,121,000	$ 329,922,000	406,895,000
Number of firm capacity producers declining to provide financial information to determine primary beneficiary status | entity							2
Minimum potential number of IPP entities consolidated into company in the future | entity							1
Hawaiian Electric Company | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs					37,000,000	38,000,000	$ 97,000,000	107,000,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs					51,000,000	73,000,000	143,000,000	214,000,000
Power purchase capacity that Increases from initial capacity (in megawatts) | MW				180
Number of years entity entered under power purchase agreement				25 years
Power purchase capacity that Increases from initial capacity (in megawatts) | MW		208
Accounts payable					13,000,000		13,000,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs					13,000,000	16,000,000	34,000,000	36,000,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs					18,000,000	18,000,000	50,000,000	50,000,000
Hawaiian Electric Company | Puna Geothermal Venture
Power purchase agreement
Purchases from IPPs					8,000,000	10,000,000	22,000,000	36,000,000
Hawaiian Electric Company | Hawaiian Commercial & Sugar (HC&S)
Power purchase agreement
Purchases from IPPs					2,000,000	2,000,000	7,000,000	50,000,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs					32,000,000	36,000,000	93,000,000	53,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs					26,713,000	34,166,000	73,161,000	91,827,000
Maui Electric
Power purchase agreement
Purchases from IPPs					14,503,000	$ 16,595,000	42,726,000	47,399,000
Maui Electric | Subsequent Event
Power purchase agreement
Maximum scheduled energy during certain month (in megawatts) | MW	4
Maximum potential emergency power | MW	16
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures					51,500,000		51,500,000		51,500,000
Interest income							$ 2,500,000	2,500,000
HECO Capital Trust III | Hawaiian Electric Company
Unconsolidated variable interest entities
Principal amount of 2004 Debentures			$ 31,500,000
Percent of ownership in Trust III							100.00%
HECO Capital Trust III | Hawaiian Electric Company | 2004 Trust Preferred Securities
Unconsolidated variable interest entities
Number of 2004 Trust Preferred Securities issued | security			2,000,000
Dividend rate on 2004 Trust Preferred Securities (as a percent)			6.50%
Aggregate Liquidation preference			$ 50,000,000
Balance of Trust Securities					50,000,000		$ 50,000,000		50,000,000
Dividend distributions on Trust Preferred Securities							2,400,000	2,400,000
HECO Capital Trust III | Hawaiian Electric Company | Trust Common Securities
Unconsolidated variable interest entities
Aggregate Liquidation preference			1,500,000
Balance of Trust Securities					$ 1,500,000		1,500,000		$ 1,500,000
Common dividend							$ 75,000	$ 75,000
HECO Capital Trust III | Hawaii Electric Light Company, Inc. (HELCO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures			10,000,000
HECO Capital Trust III | Maui Electric
Unconsolidated variable interest entities
Principal amount of 2004 Debentures			$ 10,000,000