Electric utility segment - Unconsolidated variable interest entities (Details)	1 Months Ended						3 Months Ended		6 Months Ended
	Nov. 30, 2015 MW	Oct. 31, 2015 MW	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	Oct. 31, 1988 MW	Mar. 31, 1988 MW	Jun. 30, 2016 USD ($) entity	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) agreement entity MW	Jun. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)
Power purchase agreement
Purchases from IPPs							$ 139,000,000	$ 149,000,000	$ 255,000,000	$ 285,000,000
Termination period									60 days
Accounts payable							$ 130,160,000		$ 130,160,000		$ 138,523,000
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs) | agreement									5
Maximum capacity of small power production facilities (in kilowatts) | MW									0.1
Number of entities currently not required to be consolidated as VIEs | entity							0		0
Purchases from IPPs							$ 103,062,000	107,370,000	$ 194,979,000	210,620,000
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							36,000,000	26,000,000	$ 74,000,000	60,000,000
Power purchase capacity that Increases from initial capacity (in megawatts) | MW	189					180
Number of years entity entered under power purchase agreement						30 years
Accounts payable							13,000,000		13,000,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs							36,000,000	48,000,000	65,000,000	92,000,000
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							10,000,000		10,000,000
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs							4,000,000	10,000,000	15,000,000	21,000,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs							17,000,000	16,000,000	33,000,000	32,000,000
Hawaiian Electric Company | Puna Geothermal Venture
Power purchase agreement
Purchases from IPPs							5,000,000	7,000,000	12,000,000	14,000,000
Hawaiian Electric Company | Hawaiian Commercial & Sugar (HC&S)
Power purchase agreement
Purchases from IPPs							0	3,000,000	0	5,000,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs							41,000,000	39,000,000	56,000,000	61,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs							19,360,000	24,555,000	36,157,000	46,448,000
Maui Electric
Power purchase agreement
Purchases from IPPs							16,636,000	$ 17,359,000	23,781,000	28,223,000
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									$ 1,700,000	1,700,000
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									1,600,000	1,600,000
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									$ 50,000	$ 50,000
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