Shareholders' equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,344,841	$ 2,202,499
Current period other comprehensive income (loss)	(9,801)	20,488
Ending balance	2,377,380	2,237,955
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(289,350)	(336,028)
Current period other comprehensive income (loss)	(9,801)	20,488
Ending balance	(299,151)	(315,540)
Net unrealized gains (losses) on securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(282,963)	(328,904)
Current period other comprehensive income (loss)	(10,503)	20,282
Ending balance	(293,466)	(308,622)
Unrealized gains (losses) on derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	1,638	1,991
Current period other comprehensive income (loss)	692	138
Ending balance	2,330	2,129
Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(8,025)	(9,115)
Current period other comprehensive income (loss)	10	68
Ending balance	(8,015)	(9,047)
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,409,110	2,344,170
Current period other comprehensive income (loss)	(49)	(45)
Ending balance	2,435,282	2,358,884
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,849	2,861
Current period other comprehensive income (loss)	(49)	(45)
Ending balance	2,800	2,816
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,849	2,861
Current period other comprehensive income (loss)	(49)	(45)
Ending balance	$ 2,800	$ 2,816