Consolidating financial information (Details 2) - HECO (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Net income (loss) for common stock	$ 33,679	$ 38,316
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	6,021	3,873
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	(5,313)	(3,395)
Other comprehensive income (loss), net of taxes	(61)	311
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	33,618	38,627
HECO
Net income (loss) for common stock	24,429	27,300
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	5,331	3,472
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	(5,313)	(3,395)
Other comprehensive income (loss), net of taxes	18	77
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	24,447	27,377
HELCO
Net income (loss) for common stock	4,420	6,611
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	759	532
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	(761)	(526)
Other comprehensive income (loss), net of taxes	(2)	6
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	4,418	6,617
MECO
Net income (loss) for common stock	6,565	1,880
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	657	473
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	(656)	(467)
Other comprehensive income (loss), net of taxes	1	6
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	6,566	1,886
Other subsidiaries
Net income (loss) for common stock		(1)
Retirement benefit plans:
Comprehensive income attributable to Hawaiian Electric Industries, Inc.		(1)
Consolidating adjustments
Net income (loss) for common stock	(10,985)	(8,490)
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	(1,416)	(1,005)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	1,417	993
Other comprehensive income (loss), net of taxes	1	(12)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(10,984)	(8,502)
HECO Consolidated
Net income (loss) for common stock	24,429	27,300
Retirement benefit plans:
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	5,331	3,472
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of tax benefits	(5,313)	(3,395)
Other comprehensive income (loss), net of taxes	18	77
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 24,447	$ 27,377