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		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	$ 79,406	$ 63,661	$ 155,222	$ 127,036
Income taxes on regulated activities	(22,824)	(13,742)	(44,122)	(29,806)
Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	61,496	42,518	118,750	87,726
Income taxes on regulated activities	(18,626)	(11,080)	(36,034)	(22,659)
Hawaiian Electric Company, Inc. and Subsidiaries
Operating income	28,297	14,395	53,233	30,285
Hawaiian Electric Company, Inc. and Subsidiaries | Electric utility
Operating income from regulated and nonregulated activities before income taxes (per HEI consolidated statements of income)	61,496	42,518	118,750	87,726
Income taxes on regulated activities	(18,574)	(11,160)	(35,939)	(22,770)
Revenues from nonregulated activities	(1,867)	(1,086)	(3,539)	(2,120)
Add: Expenses from nonregulated activities	452	268	816	423
Operating income	$ 41,507	$ 30,540	$ 80,088	$ 63,259