Electric utility segment Consolidating Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income for common stock	$ 33,157	$ 47,815	$ 41,421	$ 45,927	$ 39,013	$ 48,236	$ 40,588	$ 33,679	$ 168,320	$ 161,516	$ 138,658
Net gains (losses) arising during the period, net of (taxes) benefits									(234,166)	223,177	(99,159)
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									11,344	23,280	15,291
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									207,833	(222,595)	75,471
Other comprehensive income (loss), net of taxes									(10,628)	9,673	(7,286)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									157,692	171,189	131,372
HECO
Net income for common stock									137,641	122,929	99,276
Net gains (losses) arising during the period, net of (taxes) benefits									(218,608)	203,479	(90,082)
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									10,212	20,694	13,673
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									207,833	(222,595)	75,471
Other comprehensive income (loss), net of taxes									(563)	1,578	(938)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									137,078	124,507	98,338
HELCO
Net income for common stock									18,689	20,136	16,212
Net gains (losses) arising during the period, net of (taxes) benefits									(28,725)	30,542	(13,577)
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									1,270	2,880	2,101
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									27,437	(33,277)	11,442
Other comprehensive income (loss), net of taxes									(18)	145	(34)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									18,671	20,281	16,178
MECO
Net income for common stock									22,275	21,277	12,627
Net gains (losses) arising during the period, net of (taxes) benefits									(29,352)	27,820	(10,935)
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									1,090	2,557	1,771
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									28,257	(30,254)	9,093
Other comprehensive income (loss), net of taxes									(5)	123	(71)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									22,270	21,400	12,556
Other subsidiaries
Net income for common stock									0	(3)	(3)
Net gains (losses) arising during the period, net of (taxes) benefits											0
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits											0
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes											0
Other comprehensive income (loss), net of taxes											0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									0	(3)	(3)
Consolidating adjustments
Net income for common stock									(40,964)	(41,410)	(28,836)
Net gains (losses) arising during the period, net of (taxes) benefits									58,077	(58,362)	24,512
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									(2,360)	(5,437)	(3,872)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									(55,694)	63,531	(20,535)
Other comprehensive income (loss), net of taxes									23	(268)	105
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									(40,941)	(41,678)	(28,731)
HECO Consolidated
Net income for common stock	$ 29,112	$ 38,879	$ 34,230	$ 35,420	$ 31,990	$ 37,817	$ 28,693	$ 24,429	137,641	122,929	99,276
Net gains (losses) arising during the period, net of (taxes) benefits									(218,608)	203,479	(90,082)
Less: amortization of transition obligation, prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits									10,212	20,694	13,673
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes									207,833	(222,595)	75,471
Other comprehensive income (loss), net of taxes									(563)	1,578	(938)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.									$ 137,078	$ 124,507	$ 98,338