Unconsolidated variable interest entities (Details) - HECO (USD $)	1 Months Ended	3 Months Ended
	Mar. 31, 2004 item	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Power purchase agreement
Purchases from IPPs		$ 153,000,000	$ 165,000,000
Accounts payable		253,096,000		212,379,000
Hawaiian Electric Company, Inc. and Subsidiaries
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%
Purchases from IPPs		111,155,000	124,780,000
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, Inc. and Subsidiaries | AES Hawaii, Inc. (AES Hawaii)
Power purchase agreement
Purchases from IPPs		23,000,000	35,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Kalaeloa Partners, L.P. (Kalaeloa)
Power purchase agreement
Purchases from IPPs		65,000,000	69,000,000
Accounts payable		24,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | Hamakua Energy Partners, L.P. (HEP)
Power purchase agreement
Purchases from IPPs		12,000,000	14,000,000
Hawaiian Electric Company, Inc. and Subsidiaries | HPOWER
Power purchase agreement
Purchases from IPPs		15,000,000	16,000,000
Hawaii Electric Light Company, Inc. (HELCO)
Power purchase agreement
Purchases from IPPs		30,122,000	33,908,000
Maui Electric Company, Limited (MECO)
Power purchase agreement
Purchases from IPPs		12,087,000	6,101,000
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, Inc. and Subsidiaries
Unconsolidated variable interest entities
Principal amount of 2004 Debentures	31,500,000
HECO Capital Trust III | Hawaiian Electric Company, Inc. and Subsidiaries | 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, Inc. and Subsidiaries | 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 Company, Limited (MECO)
Unconsolidated variable interest entities
Principal amount of 2004 Debentures	$ 10,000,000