Shareholders' equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,377,380	$ 2,344,841	$ 2,237,955	$ 2,202,499	$ 2,344,841	$ 2,202,499
Current period other comprehensive income (loss)	1,594	(9,801)	(7,609)	20,488	(8,207)	12,879
Ending balance	1,085,273	2,377,380	2,249,377	2,237,955	1,085,273	2,249,377
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(299,151)	(289,350)	(315,540)	(336,028)	(289,350)	(336,028)
Current period other comprehensive income (loss)	1,594	(9,801)	(7,609)	20,488
Ending balance	(297,557)	(299,151)	(323,149)	(315,540)	(297,557)	(323,149)
Net unrealized gains (losses) on securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(282,963)		(328,904)	(282,963)	(328,904)
Current period other comprehensive income (loss)					(8,901)	12,987
Ending balance	(291,864)		(315,917)		(291,864)	(315,917)
Unrealized gains (losses) on derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		1,638		1,991	1,638	1,991
Current period other comprehensive income (loss)					670	(245)
Ending balance	2,308		1,746		2,308	1,746
Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(8,025)		(9,115)	(8,025)	(9,115)
Current period other comprehensive income (loss)					24	137
Ending balance	(8,001)		(8,978)		(8,001)	(8,978)
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,435,282	2,409,110	2,358,884	2,344,170	2,409,110	2,344,170
Current period other comprehensive income (loss)	(46)	(49)	(44)	(45)	(95)	(89)
Ending balance	1,192,842	2,435,282	2,371,889	2,358,884	1,192,842	2,371,889
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,800	2,849	2,816	2,861	2,849	2,861
Current period other comprehensive income (loss)	(46)	(49)	(44)	(45)
Ending balance	2,754	2,800	2,772	2,816	2,754	2,772
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ 2,849		$ 2,861	2,849	2,861
Current period other comprehensive income (loss)					(95)	(89)
Ending balance	$ 2,754		$ 2,772		$ 2,754	$ 2,772