Shareholders' equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,249,377	$ 2,237,955	$ 2,202,499	$ 2,233,504	$ 2,303,642	$ 2,390,884	$ 2,202,499	$ 2,390,884
Current period other comprehensive income (loss)	(34,875)	(7,609)	20,488	(96,012)	(87,840)	(117,159)	(21,996)	(301,011)
Ending balance	2,224,354	2,249,377	2,237,955	2,162,922	2,233,504	2,303,642	2,224,354	2,162,922
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(323,149)	(315,540)	(336,028)	(257,532)	(169,692)	(52,533)	(336,028)	(52,533)
Current period other comprehensive income (loss)	(34,875)	(7,609)	20,488	(96,012)	(87,840)	(117,159)
Ending balance	(358,024)	(323,149)	(315,540)	(353,544)	(257,532)	(169,692)	(358,024)	(353,544)
Net unrealized gains (losses) on securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(328,904)			(32,037)	(328,904)	(32,037)
Current period other comprehensive income (loss)							(21,330)	(308,229)
Ending balance	(350,234)			(340,266)			(350,234)	(340,266)
Unrealized gains (losses) on derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			1,991			(3,638)	1,991	(3,638)
Current period other comprehensive income (loss)							(827)	6,561
Ending balance	1,164			2,923			1,164	2,923
Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(9,115)			(16,858)	(9,115)	(16,858)
Current period other comprehensive income (loss)							161	657
Ending balance	(8,954)			(16,201)			(8,954)	(16,201)
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,371,889	2,358,884	2,344,170	2,289,595	2,276,884	2,261,899	2,344,170	2,261,899
Current period other comprehensive income (loss)	(77)	(44)	(45)	108	51	51	(166)	210
Ending balance	2,383,023	2,371,889	2,358,884	2,307,992	2,289,595	2,276,884	2,383,023	2,307,992
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,772	2,816	2,861	(3,178)	(3,229)	(3,280)	2,861	(3,280)
Current period other comprehensive income (loss)	(77)	(44)	(45)	108	51	51
Ending balance	2,695	$ 2,772	2,816	(3,070)	$ (3,178)	(3,229)	2,695	(3,070)
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 2,861			$ (3,280)	2,861	(3,280)
Current period other comprehensive income (loss)							(166)	210
Ending balance	$ 2,695			$ (3,070)			$ 2,695	$ (3,070)