Shareholders' equity - Accumulated other comprehensive income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,233,504	$ 2,303,642	$ 2,390,884	$ 2,367,329	$ 2,321,293	$ 2,337,502	$ 2,390,884	$ 2,337,502
Current period other comprehensive income (loss)	(96,012)	(87,840)	(117,159)	(11,305)	16,472	(44,016)	(301,011)	(38,849)
Ending balance	2,162,922	2,233,504	2,303,642	2,383,543	2,367,329	2,321,293	2,162,922	2,383,543
AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(257,532)	(169,692)	(52,533)	(28,808)	(45,280)	(1,264)	(52,533)	(1,264)
Current period other comprehensive income (loss)	(96,012)	(87,840)	(117,159)	(11,305)	16,472	(44,016)
Ending balance	(353,544)	(257,532)	(169,692)	(40,113)	(28,808)	(45,280)	(353,544)	(40,113)
Net unrealized gains (losses) on securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(32,037)			19,986	(32,037)	19,986
Current period other comprehensive income (loss)							(308,229)	(40,308)
Ending balance	(340,266)			(20,322)			(340,266)	(20,322)
Unrealized gains (losses) on derivatives
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(3,638)			(3,363)	(3,638)	(3,363)
Current period other comprehensive income (loss)							6,561	1,009
Ending balance	2,923			(2,354)			2,923	(2,354)
Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(16,858)			(17,887)	(16,858)	(17,887)
Current period other comprehensive income (loss)							657	450
Ending balance	(16,201)			(17,437)			(16,201)	(17,437)
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	2,289,595	2,276,884	2,261,899	2,171,396	2,157,385	2,141,918	2,261,899	2,141,918
Current period other comprehensive income (loss)	108	51	51	106	35	34	210	175
Ending balance	2,307,992	2,289,595	2,276,884	2,193,919	2,171,396	2,157,385	2,307,992	2,193,919
Hawaiian Electric Company, Inc. and Subsidiaries | AOCI
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(3,178)	(3,229)	(3,280)	(2,850)	(2,885)	(2,919)	(3,280)	(2,919)
Current period other comprehensive income (loss)	108	51	51	106	35	34
Ending balance	(3,070)	$ (3,178)	(3,229)	(2,744)	$ (2,850)	(2,885)	(3,070)	(2,744)
Hawaiian Electric Company, Inc. and Subsidiaries | Retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ (3,280)			$ (2,919)	(3,280)	(2,919)
Current period other comprehensive income (loss)							210	175
Ending balance	$ (3,070)			$ (2,744)			$ (3,070)	$ (2,744)