Electric utility segment - Condensed consolidating statement of comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 34,193	$ 32,352
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	454	54
Effective portion of foreign currency hedge net unrealized gain, net of taxes	0	1,002
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 $2,304 and $2,061, respectively	3,921	3,538
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,613)	(3,222)
Other comprehensive income, net of taxes	985	8,800
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	35,178	41,152
Hawaiian Electric Company
Condensed Statement of Income Captions [Line Items]
Net income for common stock	21,465	25,367
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	454
Effective portion of foreign currency hedge net unrealized gain, net of taxes		1,002
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 $2,304 and $2,061, respectively	3,618	3,236
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,613)	(3,222)
Other comprehensive income, net of taxes	459	1,016
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	21,924	26,383
HELCO
Condensed Statement of Income Captions [Line Items]
Net income for common stock	4,584	3,962
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		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 $2,304 and $2,061, respectively	503	458
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(503)	(458)
Other comprehensive income, net of taxes	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	4,584	3,962
Maui Electric
Condensed Statement of Income Captions [Line Items]
Net income for common stock	4,019	3,967
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		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 $2,304 and $2,061, respectively	466	418
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(467)	(418)
Other comprehensive income, net of taxes	(1)	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	4,018	3,967
Other subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	0	0
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		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 $2,304 and $2,061, respectively	0	0
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	0	0
Other comprehensive income, net of taxes	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	0	0
Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(8,603)	(7,929)
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes		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 $2,304 and $2,061, respectively	(969)	(876)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	970	876
Other comprehensive income, net of taxes	1	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(8,602)	(7,929)
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	21,465	25,367
Derivatives qualifying as cash flow hedges:
Reclassification adjustment to net income, net of tax benefits	454	0
Effective portion of foreign currency hedge net unrealized gain, net of taxes	0	1,002
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 $2,304 and $2,061, respectively	3,618	3,236
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(3,613)	(3,222)
Other comprehensive income, net of taxes	459	1,016
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 21,924	$ 26,383