Electric utility segment - Consolidating Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Condensed Statement of Income Captions [Line Items]
Net income for common stock	$ 246,166	$ 197,824	$ 217,882
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	153,121	(60,529)	10,914
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	19,253	23,689	10,107
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	(171,345)	39,860	(16,177)
Other comprehensive loss, net of tax benefits	(51,269)	18,775	30,571
Comprehensive income	194,897	216,599	248,453
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Statement of Income Captions [Line Items]
Net income for common stock	177,642	169,340	156,840
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	151,523	(63,050)	5,249
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	19,461	21,550	9,550
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	(171,345)	39,860	(16,177)
Other comprehensive loss, net of tax benefits	(361)	(1,640)	(1,378)
Comprehensive income	177,281	167,700	155,462
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaiian Electric (parent only)
Condensed Statement of Income Captions [Line Items]
Net income for common stock	177,642	169,340	156,840
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	151,523	(63,050)	5,249
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	19,461	21,550	9,550
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	(171,345)	39,860	(16,177)
Other comprehensive loss, net of tax benefits	(361)	(1,640)	(1,378)
Comprehensive income	177,281	167,700	155,462
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaii Electric Light
Condensed Statement of Income Captions [Line Items]
Net income for common stock	21,180	27,493	20,817
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	17,902	(9,424)	373
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	2,749	3,179	1,455
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	(20,585)	6,025	(1,840)
Other comprehensive loss, net of tax benefits	66	(220)	(12)
Comprehensive income	21,246	27,273	20,805
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Maui Electric
Condensed Statement of Income Captions [Line Items]
Net income for common stock	24,173	20,011	22,350
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	16,572	(10,897)	(204)
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	2,553	2,763	1,182
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	(18,898)	8,000	(1,152)
Other comprehensive loss, net of tax benefits	227	(134)	(174)
Comprehensive income	24,400	19,877	22,176
Hawaiian Electric Company, Inc. and Subsidiaries | Consolidating adjustments
Condensed Statement of Income Captions [Line Items]
Net income for common stock	(45,353)	(47,504)	(43,167)
Retirement benefit plans:
Net gains (losses) arising during the period, net of (taxes) benefits	(34,474)	20,321	(169)
Adjustment for amortization of prior service credit and net losses recognized during the period in net periodic benefit cost, net of tax benefits	(5,302)	(5,942)	(2,637)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of (taxes) benefits	39,483	(14,025)	2,992
Other comprehensive loss, net of tax benefits	(293)	354	186
Comprehensive income	$ (45,646)	$ (47,150)	$ (42,981)