Consolidating financial information (Details 2) - 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
Net income (loss) for common stock	$ 38,800	$ 27,139	$ 77,116	$ 55,601
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	3,768	2,449	7,641	3,488
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,289)	(2,105)	(6,684)	(4,352)
Other comprehensive income, net of taxes	1,550	4,467	1,861	2,629
Comprehensive income attributable to common shareholders	40,350	31,606	78,977	58,230
HECO
Net income (loss) for common stock	29,376	17,024	56,676	36,213
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	3,364	2,152	6,836	4,426
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,289)	(2,105)	(6,684)	(4,352)
Other comprehensive income, net of taxes	75	47	152	74
Comprehensive income attributable to common shareholders	29,451	17,071	56,828	36,287
HELCO
Net income (loss) for common stock	4,491	6,575	11,102	13,192
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	518	339	1,050	696
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(511)	(338)	(1,037)	(695)
Other comprehensive income, net of taxes	7	1	13	1
Comprehensive income attributable to common shareholders	4,498	6,576	11,115	13,193
MECO
Net income (loss) for common stock	3,760	4,389	5,640	9,267
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	412	284	885	567
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(406)	(282)	(873)	(568)
Other comprehensive income, net of taxes	6	2	12	(1)
Comprehensive income attributable to common shareholders	3,766	4,391	5,652	9,266
RHI
Net income (loss) for common stock			(1)	(2)
Other comprehensive income (loss), net of taxes:
Comprehensive income attributable to common shareholders			(1)	(2)
UBC
Net income (loss) for common stock	(1)	(1)	(1)	(4)
Other comprehensive income (loss), net of taxes:
Comprehensive income attributable to common shareholders	(1)	(1)	(1)	(4)
Reclassifications and eliminations
Net income (loss) for common stock	(8,250)	(10,963)	(16,740)	(22,453)
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	(930)	(623)	(1,935)	(1,263)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	917	620	1,910	1,263
Other comprehensive income, net of taxes	(13)	(3)	(25)
Comprehensive income attributable to common shareholders	(8,263)	(10,966)	(16,765)	(22,453)
HECO Consolidated
Net income (loss) for common stock	29,376	17,024	56,676	36,213
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	3,364	2,152	6,836	4,426
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,289)	(2,105)	(6,684)	(4,352)
Other comprehensive income, net of taxes	75	47	152	74
Comprehensive income attributable to common shareholders	$ 29,451	$ 17,071	$ 56,828	$ 36,287