Electric utility segment - Unconsolidated variable interest entities (Details)	1 Months Ended					3 Months Ended
	Aug. 31, 2012 MW	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	Oct. 31, 1988 MW	Mar. 31, 1988 MW	Mar. 31, 2017 USD ($) agreement entity	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Power purchase agreement
Purchases from IPPs						$ 127,000,000	$ 116,000,000
Termination period (in days)						60 days
Minimum power volume required (in megawatts) | MW	186				180
Accounts payable						$ 160,819,000		$ 143,279,000
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) (in agreements) | agreement						5
Number of entities currently not required to be consolidated as VIEs (in entities) | entity						0
Purchases from IPPs						$ 100,147,000	91,917,000
Number of firm capacity producers declining to provide financial information to determine primary beneficiary status (in entities) | entity						2
Minimum potential number of IPP entities consolidated into company in the future (in entities) | entity						1
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs						$ 40,000,000	29,000,000
Power purchase capacity that Increases from initial capacity (in megawatts) | MW				180
Number of years entity entered under power purchase agreement (in years)				25 years
Power purchase capacity that Increases from initial capacity (in megawatts) | MW		208
Accounts payable						11,000,000
Hawaiian Electric Company | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs						29,000,000	38,000,000
Number of years entity entered under power purchase agreement (in years)					30 years
Accounts payable						13,000,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs						17,000,000	16,000,000
Hawaiian Electric Company | Puna Geothermal Venture
Power purchase agreement
Purchases from IPPs						8,000,000	7,000,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs						7,000,000	11,000,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs						26,000,000	15,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs						18,589,000	16,797,000
Maui Electric
Power purchase agreement
Purchases from IPPs						8,388,000	$ 7,145,000
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures						51,500,000		51,500,000
Interest income						$ 800,000
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 (as a percent)						100.00%
HECO Capital Trust III | Hawaiian Electric Company | 2004 Trust Preferred Securities
Unconsolidated variable interest entities
Number of 2004 Trust Preferred Securities issued (in securities) | 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
Dividend distributions on Trust Preferred Securities						800,000
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
Common dividend						$ 25,000
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