Electric utility segment - Consolidating statement of comprehensive income (loss) (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 50,673	$ 47,808	$ 117,557	$ 134,876
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	5,611	2,829	16,850	8,515
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	(5,091)	(2,542)	(15,274)	(7,627)
Other comprehensive income (loss), net of taxes	4,430	(1,311)	5,361	2,756
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	55,103	46,497	122,918	137,632
Hawaiian Electric Company
Condensed Statement of Income Captions [Line Items]
Net income for common stock	43,006	38,879	102,721	108,529
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	5,095	2,552	15,285	7,659
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	(5,091)	(2,542)	(15,274)	(7,627)
Other comprehensive income (loss), net of taxes	4	10	11	32
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	43,010	38,889	102,732	108,561
HELCO
Condensed Statement of Income Captions [Line Items]
Net income for common stock	4,189	3,301	12,461	13,308
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	682	317	2,046	953
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	(683)	(319)	(2,050)	(955)
Other comprehensive income (loss), net of taxes	(1)	(2)	(4)	(2)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	4,188	3,299	12,457	13,306
Maui Electric
Condensed Statement of Income Captions [Line Items]
Net income for common stock	7,669	6,499	16,713	15,268
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	626	272	1,878	817
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	(627)	(272)	(1,882)	(817)
Other comprehensive income (loss), net of taxes	(1)	0	(4)	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	7,668	6,499	16,709	15,268
Other subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	0	0	0	0
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	0	0	0	0
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	0	0	0	0
Other comprehensive income (loss), net of taxes	0	0	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	0	0	0	0
Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(11,858)	(9,800)	(29,174)	(28,576)
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	(1,308)	(589)	(3,924)	(1,770)
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	1,310	591	3,932	1,772
Other comprehensive income (loss), net of taxes	2	2	8	2
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(11,856)	(9,798)	(29,166)	(28,574)
HECO Consolidated
Condensed Statement of Income Captions [Line Items]
Net income for common stock	43,006	38,879	102,721	108,529
Retirement benefit plans:
Less: amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $3,245, $1,626, $9,735 and $4,878 for the respective periods	5,095	2,552	15,285	7,659
Less: reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes of $3,243, $1,619, $9,729 and $4,858 for the respective periods	(5,091)	(2,542)	(15,274)	(7,627)
Other comprehensive income (loss), net of taxes	4	10	11	32
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 43,010	$ 38,889	$ 102,732	$ 108,561