Electric utility segment - Condensed consolidating statement of comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 38,661	$ 44,128	$ 72,854	$ 76,480
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0	0	454	54
Effective portion of foreign currency hedge net unrealized gain, net of taxes	0	(745)	0	257
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	3,930	3,698	7,851	7,236
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,581)	(3,401)	(7,194)	(6,623)
Other comprehensive income, net of taxes	2,370	2,108	3,355	10,908
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	41,031	46,236	76,209	87,388
Hawaiian Electric Company
Condensed Statement of Income Captions [Line Items]
Net income for common stock	25,644	35,857	47,109	61,224
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0		454
Effective portion of foreign currency hedge net unrealized gain, net of taxes		(745)		257
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	3,621	3,391	7,239	6,627
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,581)	(3,401)	(7,194)	(6,623)
Other comprehensive income, net of taxes	40	(755)	499	261
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	25,684	35,102	47,608	61,485
HELCO
Condensed Statement of Income Captions [Line Items]
Net income for common stock	3,632	5,220	8,216	9,182
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0		0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		0		0
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	449	401	952	859
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(448)	(402)	(951)	(860)
Other comprehensive income, net of taxes	1	(1)	1	(1)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	3,633	5,219	8,217	9,181
Maui Electric
Condensed Statement of Income Captions [Line Items]
Net income for common stock	4,304	5,663	8,323	9,630
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0		0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		0		0
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	344	357	810	775
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(343)	(359)	(810)	(777)
Other comprehensive income, net of taxes	1	(2)	0	(2)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	4,305	5,661	8,323	9,628
Other subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	0	0	0	0
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0		0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		0		0
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	0	0	0	0
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	0	0	0	0
Other comprehensive income, 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	(7,936)	(10,883)	(16,539)	(18,812)
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0		0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		0		0
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	(793)	(758)	(1,762)	(1,634)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	791	761	1,761	1,637
Other comprehensive income, net of taxes	(2)	3	(1)	3
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(7,938)	(10,880)	(16,540)	(18,809)
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	25,644	35,857	47,109	61,224
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0	0	454	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes	0	(745)	0	257
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits of $___, $2,160, $___ and $4,221, respectively	3,621	3,391	7,239	6,627
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,581)	(3,401)	(7,194)	(6,623)
Other comprehensive income, net of taxes	40	(755)	499	261
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 25,684	$ 35,102	$ 47,608	$ 61,485