Electric utility segment - Condensed consolidating statement of comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 63,872	$ 64,358	$ 48,887	$ 33,420	$ 128,230	$ 82,307
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	6,008		5,690		12,018	11,396
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)		(5,159)		(11,622)	(10,317)
Other comprehensive income (loss), net of taxes	16,472	(44,016)	(332)	18,212	(27,544)	17,880
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	80,344		48,555		100,686	100,187
Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income for common stock	41,901	43,358	42,329	23,905	85,259	66,234
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	5,846		5,184		11,691	10,368
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)		(5,159)		(11,622)	(10,317)
Other comprehensive income (loss), net of taxes	35	$ 34	25	$ 26	69	51
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	41,936		42,354		85,328	66,285
Hawaiian Electric Consolidated | Reportable Legal Entities | Hawaiian Electric Industries, Inc.
Condensed Statement of Income Captions [Line Items]
Net income for common stock	41,901		42,329		85,259	66,234
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	5,846		5,184		11,691	10,368
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(5,811)		(5,159)		(11,622)	(10,317)
Other comprehensive income (loss), net of taxes	35		25		69	51
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	41,936		42,354		85,328	66,285
Hawaiian Electric Consolidated | Reportable Legal Entities | Hawaii Electric Light
Condensed Statement of Income Captions [Line Items]
Net income for common stock	5,607		7,179		12,299	13,246
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	834		751		1,669	1,499
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(834)		(748)		(1,668)	(1,495)
Other comprehensive income (loss), net of taxes	0		3		1	4
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	5,607		7,182		12,300	13,250
Hawaiian Electric Consolidated | Reportable Legal Entities | Maui Electric
Condensed Statement of Income Captions [Line Items]
Net income for common stock	5,137		6,597		10,955	9,334
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		650		1,522	1,302
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(761)		(653)		(1,522)	(1,305)
Other comprehensive income (loss), net of taxes	0		(3)		0	(3)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	5,137		6,594		10,955	9,331
Hawaiian Electric Consolidated | Reportable Legal Entities | Other subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	0		0		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		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 (loss), net of taxes	0		0		0	0
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	0		0		0	0
Hawaiian Electric Consolidated | Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(10,744)		(13,776)		(23,254)	(22,580)
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	(1,595)		(1,401)		(3,191)	(2,801)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	1,595		1,401		3,190	2,800
Other comprehensive income (loss), net of taxes	0		0		(1)	(1)
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	$ (10,744)		$ (13,776)		$ (23,255)	$ (22,581)