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
	Mar. 31, 2012	Mar. 31, 2011
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	$ 75,816	$ 63,375
Income taxes on regulated activities	(21,298)	(16,064)
Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	57,254	45,208
Income taxes on regulated activities	(17,408)	(11,579)
Hawaiian Electric Company, Inc. and Subsidiaries
Operating income	24,936	15,890
Hawaiian Electric Company, Inc. and Subsidiaries | Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	57,254	45,208
Income taxes on regulated activities	(17,365)	(11,610)
Revenues from nonregulated activities	(1,672)	(1,034)
Add: Expenses from nonregulated activities	364	155
Operating income	$ 38,581	$ 32,719