Electric utility segment - Unconsolidated variable interest entities (Details)	1 Months Ended			3 Months Ended		6 Months Ended
	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	Oct. 31, 1988 MW	Jun. 30, 2017 USD ($) entity	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) agreement entity	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Power purchase agreement
Purchases from IPPs				$ 153,000,000	$ 139,000,000	$ 280,000,000	$ 255,000,000
Termination period (in days)						60 days
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) (in agreements) | agreement						5
Number of entities currently required to be consolidated as VIEs (in entities) | entity				0		0
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
Purchases from IPPs				$ 116,458,000	103,062,000	$ 216,605,000	194,979,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs				48,000,000	36,000,000	88,000,000	65,000,000
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	208,000
Hawaiian Electric Company | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs				35,000,000	36,000,000	64,000,000	74,000,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs				16,000,000	17,000,000	33,000,000	33,000,000
Hawaiian Electric Company | Puna Geothermal Venture
Power purchase agreement
Purchases from IPPs				10,000,000	5,000,000	18,000,000	12,000,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs				10,000,000	4,000,000	17,000,000	15,000,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs				34,000,000	41,000,000	60,000,000	56,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs				23,482,000	19,360,000	42,071,000	36,157,000
Maui Electric
Power purchase agreement
Purchases from IPPs				13,127,000	$ 16,636,000	21,515,000	$ 23,781,000
Variable Interest Entity, Not Primary Beneficiary
Unconsolidated variable interest entities
Investment in 2004 Debentures				51,500,000		51,500,000		$ 51,500,000
Interest income						$ 1,700,000
Variable Interest Entity, Not Primary Beneficiary | 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%
Variable Interest Entity, Not Primary Beneficiary | 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		50,000,000
Dividend distributions on Trust Preferred Securities						1,600,000
Variable Interest Entity, Not Primary Beneficiary | 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						$ 50,000
Variable Interest Entity, Not Primary Beneficiary | Hawaii Electric Light Company, Inc. (HELCO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		10,000,000
Variable Interest Entity, Not Primary Beneficiary | Maui Electric
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 10,000,000