Unconsolidated variable interest entities (Details)	1 Months Ended			12 Months Ended
	Oct. 31, 2004 MW	Mar. 31, 2004 USD ($) security	May. 31, 1991 MW	Dec. 31, 2014 USD ($) entity agreement kW	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)
Power purchase agreement
Number of power purchase agreements (PPAs) | agreement				7
Number of largest IPP's declining to provide financial information to determine primary beneficiary status | entity				3
Accounts payable				$ 186,425,000	$ 212,331,000
Hawaiian Electric Company, Inc. and Subsidiaries
Power purchase agreement
Purchases from IPPs				722,008,000	710,681,000	$ 724,240,000
Hawaiian Electric Company, Inc. and Subsidiaries | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs				145,000,000	134,000,000	146,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs				279,000,000	301,000,000	310,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs				51,000,000	51,000,000	65,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | HPOWER
Power purchase agreement
Purchases from IPPs				66,000,000	61,000,000	65,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Other IPPs
Power purchase agreement
Purchases from IPPs				$ 181,000,000	164,000,000	138,000,000
HECO
Power purchase agreement
Number of power purchase agreements (PPAs) | agreement				7
Maximum capacity of small power production facilities (in kilowatts) | kW				100
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%
Purchases from IPPs				$ 537,821,000	527,839,000	540,802,000
Number of entities owning wind farms not required to be consolidated as VIE's | entity				2
Minimum potential number of IPP entities consolidated into company in the future | entity				1
HECO | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Power purchase 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
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs				123,226,000	128,368,000	145,386,000
Maui Electric Company, Limited (MECO)
Power purchase agreement
Purchases from IPPs				60,961,000	$ 54,474,000	$ 38,052,000
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures				51,500,000
Interest income				3,400,000
HECO Capital Trust III | HECO
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 31,500,000.0
HECO Capital Trust III | HECO | 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
Dividend distributions on Trust Preferred Securities				3,300,000
HECO Capital Trust III | HECO | Trust Common Securities
Unconsolidated variable interest entities
Aggregate Liquidation preference		1,500,000.0
Balance of Trust Securities				1,500,000
Common dividend				$ 100,000
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 Company, Limited (MECO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures		$ 10,000,000