Reconciliation of electric utility operating income per HEI and HECO consolidated statements of income (Details) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	$ 91,702	$ 94,490	$ 246,924	$ 221,526
Income taxes on regulated activities	(25,804)	(27,894)	(69,926)	(57,700)
Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	74,819	74,956	193,569	162,682
Income taxes on regulated activities	(22,395)	(23,787)	(58,429)	(46,446)
Hawaiian Electric Company, Inc. and Subsidiaries
Operating income	35,300	32,859	88,533	63,144
Hawaiian Electric Company, Inc. and Subsidiaries | Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	74,819	74,956	193,569	162,682
Income taxes on regulated activities	(22,352)	(23,860)	(58,291)	(46,630)
Revenues from nonregulated activities	(1,892)	(1,347)	(5,431)	(3,467)
Add: Expenses from nonregulated activities	804	250	1,620	673
Operating income	$ 51,379	$ 49,999	$ 131,467	$ 113,258