Electric utility subsidiary - Unconsolidated variable interest entities (Details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Oct. 31, 2004 MW	May 31, 1991 MW	Oct. 31, 1988	Mar. 31, 2004 security	Dec. 31, 2014
Power purchase agreement
Purchases from IPPs	$ 136,000,000	$ 165,000,000
Accounts payable	167,784,000						186,425,000
Hawaiian Electric Company
Power purchase agreement
Number of power purchase agreements (PPAs)	6
Maximum capacity of small power production facilities (in kilowatts)	100
Number of entities currently not required to be consolidated as VIEs	0
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%
Variable Interest Entity, Unavailability of Information, Number of Entities	3
Purchases from IPPs	103,250,000	123,969,000
Number of firm capacity producers declining to provide financial information to determine primary beneficiary status	2
Minimum potential number of IPP entities consolidated into company in the future	1
Hawaiian Electric Company | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs	34,000,000	33,000,000
Hawaiian Electric Company | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs	44,000,000	67,000,000
Power purchase capacity that Increases from initial 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
Hawaiian Electric Company | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs	11,000,000	12,000,000
Hawaiian Electric Company | HPOWER
Power purchase agreement
Purchases from IPPs	16,000,000	16,000,000
Hawaiian Electric Company | Other IPPs
Power purchase agreement
Purchases from IPPs	31,000,000	37,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs	21,893,000	29,491,000
Maui Electric
Power purchase agreement
Purchases from IPPs	10,864,000	11,456,000
HECO Capital Trust III
Unconsolidated variable interest entities
Investment in 2004 Debentures	51,500,000						51,500,000
Interest income	800,000	800,000
HECO Capital Trust III | Hawaiian Electric Company
Unconsolidated variable interest entities
Principal amount of 2004 Debentures						31,500,000
HECO Capital Trust III | Hawaiian Electric Company | 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						50,000,000
Dividend distributions on Trust Preferred Securities	800,000	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	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