Electric utility segment - Condensed consolidating statement of comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 64,358	$ 33,420
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	6,010	5,706
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)	(5,158)
Other comprehensive income (loss), net of taxes	(44,016)	18,212
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	20,342	51,632
Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(12,510)	(8,804)
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	(1,596)	(1,400)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	1,595	1,399
Other comprehensive income (loss), net of taxes	(1)	(1)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(12,511)	(8,805)
Hawaiian Electric (parent only) | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	43,358	23,905
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	5,845	5,184
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)	(5,158)
Other comprehensive income (loss), net of taxes	34	26
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	43,392	23,931
Hawaii Electric Light | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	6,692	6,067
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	835	748
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(834)	(747)
Other comprehensive income (loss), net of taxes	1	1
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	6,693	6,068
Maui Electric | Reportable Legal Entities
Condensed Statement of Income Captions [Line Items]
Net income for common stock	5,818	2,737
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	761	652
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(761)	(652)
Other comprehensive income (loss), net of taxes	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	5,818	2,737
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 taxes	0	0
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	0	0
Other comprehensive income (loss), net of taxes	0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	0	0
Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income for common stock	43,358	23,905
Retirement benefit plans:
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of taxes	5,845	5,184
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)	(5,158)
Other comprehensive income (loss), net of taxes	34	26
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ 43,392	$ 23,931