Electric utility segment - Condensed Consolidating Statement of Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	$ 30,747			$ (104,402)			$ 83,503	$ (1,357,764)
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	(540)			(1,244)			(1,553)	(2,138)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	552			1,333			1,519	2,251
Other comprehensive income (loss), net of taxes	(734)	$ (306)	$ (460)	39,360	$ 1,594	$ (9,801)	(1,500)	31,153
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	30,013			(65,042)			82,003	(1,326,611)
Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	36,988			(82,585)			123,954	(1,272,758)
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	(576)			(1,331)			(1,637)	(2,344)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	552			1,333			1,519	2,251
Other comprehensive income (loss), net of taxes	(24)	$ (47)	$ (47)	2	$ (46)	$ (49)	(118)	(93)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	36,964			(82,583)			123,836	(1,272,851)
Consolidating adjustments | Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	(6,123)			18,558			(23,615)	258,633
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	95			111			277	304
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	(90)			(106)			(241)	(275)
Other comprehensive income (loss), net of taxes	5			5			36	29
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	(6,118)			18,563			(23,579)	258,662
Hawaiian Electric | Reportable Legal Entities | Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	36,988			(82,585)			123,954	(1,272,758)
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	(576)			(1,331)			(1,637)	(2,344)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	552			1,333			1,519	2,251
Other comprehensive income (loss), net of taxes	(24)			2			(118)	(93)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	36,964			(82,583)			123,836	(1,272,851)
Hawaii Electric Light | Reportable Legal Entities | Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	5,002			(7,175)			14,298	(123,080)
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	(31)			(40)			(86)	(117)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	33			42			77	112
Other comprehensive income (loss), net of taxes	2			2			(9)	(5)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	5,004			(7,173)			14,289	(123,085)
Maui Electric | Reportable Legal Entities | Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	(466)			(12,807)			5,071	(136,977)
Retirement benefit plans:
Adjustment for amortization of net gains recognized during the period in net periodic benefit cost, net of taxes	(64)			(71)			(191)	(187)
Reclassification adjustment for impact of D&Os of the PUC included in regulatory assets, net of taxes	57			64			164	163
Other comprehensive income (loss), net of taxes	(7)			(7)			(27)	(24)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	(473)			(12,814)			5,044	(137,001)
Other subsidiaries | Reportable Legal Entities | Hawaiian Electric Consolidated
Condensed Statement of Income Captions [Line Items]
Net income (loss) for common stock	1,587			1,424			4,246	1,424
Retirement benefit plans:
Adjustment for amortization of net gains 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 (loss) attributable to Hawaiian Electric Industries, Inc.	$ 1,587			$ 1,424			$ 4,246	$ 1,424