Consolidating financial information (Details 4) - 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
Balance			$ 1,528,706	$ 1,480,394
Net income (loss) for common stock	47,706	48,404	124,822	104,005
Other comprehensive income (loss), net of taxes (tax benefits)	1,586	3,181	3,447	5,810
Common stock dividends			(89,902)	(88,750)
Balance	1,607,135	1,534,515	1,607,135	1,534,515
HECO
Balance			1,402,841	1,334,155
Net income (loss) for common stock	38,375	37,959	95,051	74,172
Other comprehensive income (loss), net of taxes (tax benefits)	77	122	229	196
Common stock dividends			(54,783)	(52,919)
Balance	1,443,338	1,355,604	1,443,338	1,355,604
HELCO
Balance			280,468	269,986
Net income (loss) for common stock	4,728	7,988	15,830	21,180
Other comprehensive income (loss), net of taxes (tax benefits)	5	11	18	12
Common stock dividends			(9,854)	(12,093)
Balance	286,462	279,085	286,462	279,085
MECO
Balance			235,568	229,651
Net income (loss) for common stock	6,558	3,943	12,198	13,210
Other comprehensive income (loss), net of taxes (tax benefits)	7	20	19	19
Common stock dividends			(6,560)	(9,003)
Balance	241,225	233,877	241,225	233,877
Other subsidiaries
Balance			107	91
Net income (loss) for common stock	(1)	(2)	(3)	(8)
Capital contribution from parent				25
Balance	104	108	104	108
Consolidating adjustments
Balance			(516,143)	(499,728)
Net income (loss) for common stock	(11,285)	(11,929)	(28,025)	(34,382)
Other comprehensive income (loss), net of taxes (tax benefits)	(12)	(31)	(37)	(31)
Common stock dividends			16,414	21,096
Capital contribution from parent				(25)
Balance	(527,791)	(513,070)	(527,791)	(513,070)
HECO Consolidated
Balance			1,402,841	1,334,155
Net income (loss) for common stock	38,375	37,959	95,051	74,172
Other comprehensive income (loss), net of taxes (tax benefits)	77	122	229	196
Common stock dividends			(54,783)	(52,919)
Balance	$ 1,443,338	$ 1,355,604	$ 1,443,338	$ 1,355,604