Consolidating financial information (Details 2) - 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
Net income (loss) for common stock	$ 47,706	$ 48,404	$ 124,822	$ 104,005
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	3,826	2,068	11,467	5,556
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,342)	(1,732)	(10,026)	(6,084)
Other comprehensive income, net of taxes	1,586	3,181	3,447	5,810
Comprehensive income attributable to common shareholders	49,292	51,585	128,269	109,815
HECO
Net income (loss) for common stock	38,375	37,959	95,051	74,172
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	3,419	1,854	10,255	6,280
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,342)	(1,732)	(10,026)	(6,084)
Other comprehensive income, net of taxes	77	122	229	196
Comprehensive income attributable to common shareholders	38,452	38,081	95,280	74,368
HELCO
Net income (loss) for common stock	4,728	7,988	15,830	21,180
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	526	296	1,576	992
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(521)	(285)	(1,558)	(980)
Other comprehensive income, net of taxes	5	11	18	12
Comprehensive income attributable to common shareholders	4,733	7,999	15,848	21,192
MECO
Net income (loss) for common stock	6,558	3,943	12,198	13,210
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	443	301	1,328	868
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(436)	(281)	(1,309)	(849)
Other comprehensive income, net of taxes	7	20	19	19
Comprehensive income attributable to common shareholders	6,565	3,963	12,217	13,229
Other subsidiaries
Net income (loss) for common stock	(1)	(2)	(3)	(8)
Other comprehensive income (loss), net of taxes:
Comprehensive income attributable to common shareholders	(1)	(2)	(3)	(8)
Consolidating adjustments
Net income (loss) for common stock	(11,285)	(11,929)	(28,025)	(34,382)
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	(969)	(597)	(2,904)	(1,860)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	957	566	2,867	1,829
Other comprehensive income, net of taxes	(12)	(31)	(37)	(31)
Comprehensive income attributable to common shareholders	(11,297)	(11,960)	(28,062)	(34,413)
HECO Consolidated
Net income (loss) for common stock	38,375	37,959	95,051	74,172
Other comprehensive income (loss), net of taxes:
Less: amortization of net loss, prior service gain and transition obligation included in net periodic benefit cost, net of tax benefits	3,419	1,854	10,255	6,280
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,342)	(1,732)	(10,026)	(6,084)
Other comprehensive income, net of taxes	77	122	229	196
Comprehensive income attributable to common shareholders	$ 38,452	$ 38,081	$ 95,280	$ 74,368