Shareholders' equity - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
AOCI Attributable to Parent [Roll Forward]
Beginning balance	$ 2,337,502	$ 2,280,260	$ 2,162,280
Current period other comprehensive income (loss) and reclassifications, net of taxes	(51,269)	18,775	30,571
Ending balance	2,390,884	2,337,502	2,280,260
Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent [Roll Forward]
Beginning balance	2,141,918	2,047,352	1,957,641
Current period other comprehensive income (loss) and reclassifications, net of taxes	(361)	(1,640)	(1,378)
Ending balance	2,261,899	2,141,918	2,047,352
AOCI
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(1,264)	(20,039)	(50,610)
Current period other comprehensive income (loss) and reclassifications, net of taxes	(51,269)	18,775	30,571
Ending balance	(52,533)	(1,264)	(20,039)
AOCI | Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(2,919)	(1,279)	99
Current period other comprehensive income (loss) and reclassifications, net of taxes	(361)	(1,640)	(1,378)
Ending balance	(3,280)	(2,919)	(1,279)
Net unrealized gains (losses) on securities
AOCI Attributable to Parent [Roll Forward]
Beginning balance	19,986	2,481	(24,423)
Current period other comprehensive income (loss) and reclassifications, net of taxes	(52,023)	17,505	26,904
Ending balance	(32,037)	19,986	2,481
Unrealized gains (losses) on derivatives
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(3,363)	(1,613)	(436)
Current period other comprehensive income (loss) and reclassifications, net of taxes	(275)	(1,750)	(1,177)
Ending balance	(3,638)	(3,363)	(1,613)
Retirement benefit plans
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(17,887)	(20,907)	(25,751)
Current period other comprehensive income (loss) and reclassifications, net of taxes	1,029	3,020	4,844
Ending balance	(16,858)	(17,887)	(20,907)
Retirement benefit plans | Hawaiian Electric Company, Inc. and Subsidiaries
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(2,919)	(1,279)	99
Current period other comprehensive income (loss) and reclassifications, net of taxes	(361)	(1,640)	(1,378)
Ending balance	$ (3,280)	$ (2,919)	$ (1,279)