Electric utility subsidiary - Unconsolidated variable interest entities (Details) $ in Thousands	1 Months Ended				3 Months Ended
	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	May. 31, 1991 MW	Oct. 31, 1988	Mar. 31, 2015 USD ($) agreement entity kW	Mar. 31, 2014 USD ($)	Dec. 31, 2014 USD ($)
Power purchase agreement
Purchases from IPPs					$ 136,000	$ 165,000
Accounts payable					$ 167,784		$ 186,425
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
Percentage of power purchase from AES Hawaii, Inc. (AES Hawaii), Kalaeloa Partners, L.P. (Kalaeloa), Hamakua Energy Partners, L.P. (HEP) and HPOWER					90.00%
Variable Interest Entity, Unavailability of Information, Number of Entities | entity					3
Purchases from IPPs					$ 103,250	123,969
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					$ 34,000	33,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs					44,000	67,000
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
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs					11,000	12,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs					16,000	16,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs					31,000	37,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs					21,893	29,491
Maui Electric
Power purchase agreement
Purchases from IPPs					10,864	11,456
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures					51,500		51,500
Interest income					800	800
HECO Capital Trust III | Hawaiian Electric Company
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 31,500
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
Balance of Trust Securities					50,000		50,000
Dividend distributions on Trust Preferred Securities					800	800
HECO Capital Trust III | Hawaiian Electric Company | Trust Common Securities
Unconsolidated variable interest entities
Aggregate Liquidation preference		1,500
Balance of Trust Securities					1,500		$ 1,500
Common dividend					$ 25	$ 25
HECO Capital Trust III | Hawaii Electric Light Company, Inc. (HELCO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		10,000
HECO Capital Trust III | Maui Electric
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 10,000