Unconsolidated variable interest entities (Details) (USD $)	12 Months Ended			1 Months Ended
	Dec. 31, 2014 entity agreement	Dec. 31, 2013	Dec. 31, 2012	Oct. 31, 2004 MW	May 31, 1991 MW	Mar. 31, 2004 security
Power purchase agreement
Number of power purchase agreements (PPAs)	7
Number of largest IPP's declining to provide financial information to determine primary beneficiary status	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)	7
Maximum capacity of small power production facilities (in kilowatts)	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	2
Minimum potential number of IPP entities consolidated into company in the future	1
HECO | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Power purchase capacity (in megawatts)					180
Number of years entity entered under power purchase agreement	25 years
Power purchase capacity that Increases from initial capacity (in megawatts)				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						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