Electric utility segment - Condensed consolidating statement of comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 33,420	$ 45,688
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	5,706	2,503
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,158)	(2,298)
Other comprehensive income, net of taxes	18,212	9,241
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	51,632	54,929
Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(8,804)	(11,849)
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	(1,400)	(641)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	1,399	640
Other comprehensive income, net of taxes	(1)	(1)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(8,805)	(11,850)
Hawaiian Electric (parent only) | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	23,905	32,126
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	5,184	2,322
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,158)	(2,298)
Other comprehensive income, net of taxes	26	24
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	23,931	32,150
HELCO | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	6,067	5,169
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	748	352
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(747)	(351)
Other comprehensive income, net of taxes	1	1
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	6,068	5,170
Maui Electric | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	2,737	6,680
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	652	289
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(652)	(289)
Other comprehensive income, net of taxes	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	2,737	6,680
Other subsidiaries | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	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	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
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	23,905	32,126
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	5,184	2,322
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,158)	(2,298)
Other comprehensive income, net of taxes	26	24
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 23,931	$ 32,150