Unconsolidated variable interest entities (Details) - HECO (USD $)	9 Months Ended			3 Months Ended	9 Months Ended			9 Months Ended				9 Months Ended					3 Months Ended		9 Months Ended
	Sep. 30, 2011	Dec. 31, 2010	Mar. 31, 2004 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III	Mar. 31, 2004 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III 2004 Trust Preferred Securities securities	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III 2004 Trust Preferred Securities	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III 2004 Trust Preferred Securities	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III 2004 Trust Preferred Securities	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III Trust Common Securities	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III Trust Common Securities	Dec. 31, 2010 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III Trust Common Securities	Mar. 31, 2004 Hawaiian Electric Company, Inc. and Subsidiaries HECO Capital Trust III Trust Common Securities	Sep. 30, 2011 HECO Capital Trust III	Sep. 30, 2010 HECO Capital Trust III	Dec. 31, 2010 HECO Capital Trust III	Mar. 31, 2004 HECO Capital Trust III Hawaii Electric Light Company, Inc. (HELCO)	Mar. 31, 2004 HECO Capital Trust III Maui Electric Company, Limited (MECO)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries kW agreements mW	Sep. 30, 2010 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries AES Hawaii, Inc. (AES Hawaii)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Kalaeloa Partners, L.P. (Kalaeloa)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Hamakua Energy Partners, L.P. (HEP)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries HPOWER
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							$ 1,500,000
Principal amount of 2004 Debentures			31,500,000												10,000,000	10,000,000
Investment in 2004 Debentures												51,500,000		51,500,000
Balance of Trust Securities	1,537,758,000	1,483,637,000						1,500,000		1,500,000
Balance of Trust Securities					50,000,000		50,000,000
Interest income												2,500,000	2,500,000
Dividend distributions on Trust Preferred Securities					2,400,000	2,400,000
Common dividend								100,000	100,000
Power purchase agreement
Number of power purchase agreements (PPAs)																			6
Power purchase capacity excluding agreements with smaller IPPs (in megawatts)																			540
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 (as a percent)																			91.00%
Purchases from IPPs	$ 508,000,000																$ 188,484,000	$ 147,880,000	$ 508,179,000	$ 404,175,000	$ 106,000,000	$ 226,000,000	$ 44,000,000	$ 45,000,000