Shareholders' equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,237,955	$ 2,202,499	$ 2,303,642	$ 2,390,884	$ 2,202,499	$ 2,390,884
Current period other comprehensive income (loss)	(7,609)	20,488	(87,840)	(117,159)	12,879	(204,999)
Ending balance	2,249,377	2,237,955	2,233,504	2,303,642	2,249,377	2,233,504
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(315,540)	(336,028)	(169,692)	(52,533)	(336,028)	(52,533)
Current period other comprehensive income (loss)	(7,609)	20,488	(87,840)	(117,159)
Ending balance	(323,149)	(315,540)	(257,532)	(169,692)	(323,149)	(257,532)
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)					12,987	(209,264)
Ending balance	(315,917)		(241,301)		(315,917)	(241,301)
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)					(245)	3,911
Ending balance	1,746		273		1,746	273
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)					137	354
Ending balance	(8,978)		(16,504)		(8,978)	(16,504)
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,358,884	2,344,170	2,276,884	2,261,899	2,344,170	2,261,899
Current period other comprehensive income (loss)	(44)	(45)	51	51	(89)	102
Ending balance	2,371,889	2,358,884	2,289,595	2,276,884	2,371,889	2,289,595
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,816	2,861	(3,229)	(3,280)	2,861	(3,280)
Current period other comprehensive income (loss)	(44)	(45)	51	51
Ending balance	2,772	2,816	(3,178)	(3,229)	2,772	(3,178)
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)					(89)	102
Ending balance	$ 2,772		$ (3,178)		$ 2,772	$ (3,178)