Unconsolidated variable interest entities (Details) - HECO (USD $)	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended						1 Months Ended	9 Months Ended			9 Months Ended
	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries kilowatt item	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries AES Hawaii, Inc. (AES Hawaii)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries AES Hawaii, Inc. (AES Hawaii)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries AES Hawaii, Inc. (AES Hawaii)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries AES Hawaii, Inc. (AES Hawaii)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries Kalaeloa Partners, L.P. (Kalaeloa)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Kalaeloa Partners, L.P. (Kalaeloa)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries Kalaeloa Partners, L.P. (Kalaeloa)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Kalaeloa Partners, L.P. (Kalaeloa)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries Hamakua Energy Partners, L.P. (HEP)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Hamakua Energy Partners, L.P. (HEP)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries Hamakua Energy Partners, L.P. (HEP)	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Hamakua Energy Partners, L.P. (HEP)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries HPOWER	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries HPOWER	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries HPOWER	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries HPOWER	Sep. 30, 2012 Hawaii Electric Light Company, Inc. (HELCO)	Sep. 30, 2011 Hawaii Electric Light Company, Inc. (HELCO)	Sep. 30, 2012 Hawaii Electric Light Company, Inc. (HELCO)	Sep. 30, 2011 Hawaii Electric Light Company, Inc. (HELCO)	Sep. 30, 2012 Maui Electric Company, Limited (MECO)	Sep. 30, 2011 Maui Electric Company, Limited (MECO)	Sep. 30, 2012 Maui Electric Company, Limited (MECO)	Sep. 30, 2011 Maui Electric Company, Limited (MECO)	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2011 Hawaiian Electric Company, Inc. and Subsidiaries	Sep. 30, 2012 HECO Capital Trust III	Sep. 30, 2011 HECO Capital Trust III	Dec. 31, 2011 HECO Capital Trust III	Mar. 31, 2004 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries	Mar. 31, 2004 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries 2004 Trust Preferred Securities item	Sep. 30, 2012 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries 2004 Trust Preferred Securities	Sep. 30, 2011 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries 2004 Trust Preferred Securities	Dec. 31, 2011 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries 2004 Trust Preferred Securities	Sep. 30, 2012 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries Trust Common Securities	Sep. 30, 2011 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries Trust Common Securities	Dec. 31, 2011 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries Trust Common Securities	Mar. 31, 2004 HECO Capital Trust III Hawaiian Electric Company, Inc. and Subsidiaries Trust Common Securities	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)
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																																						50,000,000		50,000,000	1,500,000		1,500,000
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																												6
Maximum capacity of small power production facilities (in kilowatts)			100																												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%																												90.00%
Purchases from IPPs	$ 135,507,000	$ 141,742,000	$ 401,423,000	$ 386,414,000	$ 38,000,000	$ 35,000,000	$ 109,000,000	$ 106,000,000	$ 78,000,000	$ 87,000,000	$ 230,000,000	$ 226,000,000	$ 19,000,000	$ 19,000,000	$ 48,000,000	$ 44,000,000	$ 18,000,000	$ 16,000,000	$ 48,000,000	$ 45,000,000	$ 37,693,000	$ 38,252,000	$ 108,996,000	$ 100,516,000	$ 13,499,000	$ 8,490,000	$ 29,421,000	$ 21,249,000	$ 186,699,000	$ 188,484,000	$ 539,840,000	$ 508,179,000