Bank segment (HEI only) - Reconciliation of Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Gain (loss) on sales of investment securities, net and equity-method investment	$ (15,609)	$ 8,123	$ 528
Total revenues	3,682,166	3,741,985	2,850,379
Total interest expense	208,329	116,703	99,403
Less: Retirement defined benefits expense (credit)—other than service costs	(4,768)	(4,411)	(5,848)
Total expenses	3,329,562	3,360,912	2,464,313
Operating income	352,604	381,073	386,066
Add back: Retirement defined benefits expense (credit)—other than service costs	(4,768)	(4,411)	(5,848)
Add back: Loss on sale of investment securities, net	(15,609)	8,123	528
Income before income taxes	245,701	304,195	310,863
American Savings Bank (ASB)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Interest and dividend income	334,783	265,874	242,266
Noninterest income	45,410	56,972	64,660
Less: Gain on sale of real estate	495	1,778	0
Gain (loss) on sales of investment securities, net and equity-method investment	(14,965)	0	528
Total revenues	394,663	321,068	306,398
Total interest expense	82,797	13,301	5,040
Provision for credit losses	10,357	2,037	(25,825)
Noninterest expense	223,638	205,267	197,152
Less: Retirement defined benefits expense (credit)—other than service costs	(754)	(723)	(1,828)
Gain on sale of real estate	495	1,778	0
Total expenses	317,051	219,550	178,195
Operating income	77,612	101,518	128,203
Add back: Retirement defined benefits expense (credit)—other than service costs	(754)	(723)	(1,828)
Add back: Loss on sale of investment securities, net	(14,965)	0	528
Income before income taxes	$ 63,401	$ 102,241	$ 130,559