Electric utility segment - Consolidating Statements of Changes in Common Stock Equity (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Increase (decrease) in stockholders' equity
Beginning Balance				$ 2,162,280				$ 2,097,386	$ 2,162,280	$ 2,097,386	$ 2,066,753
Net income for common stock	$ 66,263	$ 63,419	$ 42,512	45,688	$ 49,573	$ 65,900	$ 46,054	40,247	217,882	201,774	165,297
Other comprehensive income (loss), net of tax benefits									30,571	(8,669)	(1,372)
Common stock dividends									(139,463)	(134,987)	(134,873)
Ending Balance	2,280,260				2,162,280				2,280,260	2,162,280	2,097,386
Parent Company
Increase (decrease) in stockholders' equity
Beginning Balance				2,162,280					2,162,280
Ending Balance	2,280,260				2,162,280				2,280,260	2,162,280
Hawaiian Electric Company, Inc. and Subsidiaries
Increase (decrease) in stockholders' equity
Beginning Balance				1,957,641				1,845,283	1,957,641	1,845,283	1,799,787
Net income for common stock	45,361	$ 46,779	$ 32,574	32,126	35,297	$ 49,712	$ 31,169	27,475	156,840	143,653	119,951
Other comprehensive income (loss), net of tax benefits									(1,378)	1,318	(688)
Issuance of common stock, net of expenses									35,501	70,692	14,000
Common stock dividends									(101,252)	(103,305)	(87,767)
Ending Balance	2,047,352				1,957,641				2,047,352	1,957,641	1,845,283
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Parent Company
Increase (decrease) in stockholders' equity
Beginning Balance				1,957,641				1,845,283	1,957,641	1,845,283	1,799,787
Net income for common stock									156,840	143,653	119,951
Other comprehensive income (loss), net of tax benefits									(1,378)	1,318	(688)
Issuance of common stock, net of expenses									35,501	70,692	14,000
Common stock dividends									(101,252)	(103,305)	(87,767)
Ending Balance	2,047,352				1,957,641				2,047,352	1,957,641	1,845,283
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Hawaii Electric Light
Increase (decrease) in stockholders' equity
Beginning Balance				295,874				286,647	295,874	286,647	291,291
Net income for common stock									20,817	24,481	20,146
Other comprehensive income (loss), net of tax benefits									(12)	34	2
Issuance of common stock, net of expenses									(1)	1	4
Common stock dividends									(17,680)	(15,289)	(24,796)
Ending Balance	298,998				295,874				298,998	295,874	286,647
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Maui Electric
Increase (decrease) in stockholders' equity
Beginning Balance				280,863				270,265	280,863	270,265	259,554
Net income for common stock									22,350	20,912	17,911
Other comprehensive income (loss), net of tax benefits									(174)	207	(55)
Issuance of common stock, net of expenses									4,899	1,498	4,801
Common stock dividends									(15,068)	(12,019)	(11,946)
Ending Balance	292,870				280,863				292,870	280,863	270,265
Hawaiian Electric Company, Inc. and Subsidiaries | Reportable Legal Entities | Other subsidiaries
Increase (decrease) in stockholders' equity
Beginning Balance				101				101	101	101	101
Net income for common stock									0	0	0
Other comprehensive income (loss), net of tax benefits									0	0	0
Issuance of common stock, net of expenses									0	0	0
Common stock dividends									0	0	0
Ending Balance	101				101				101	101	101
Hawaiian Electric Company, Inc. and Subsidiaries | Consolidating Adjustments
Increase (decrease) in stockholders' equity
Beginning Balance				$ (576,838)				$ (557,013)	(576,838)	(557,013)	(550,946)
Net income for common stock									(43,167)	(45,393)	(38,057)
Other comprehensive income (loss), net of tax benefits									186	(241)	53
Issuance of common stock, net of expenses									(4,898)	(1,499)	(4,805)
Common stock dividends									32,748	27,308	36,742
Ending Balance	$ (591,969)				$ (576,838)				$ (591,969)	$ (576,838)	$ (557,013)