Bank segment (HEI only) - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Gain on sale of investment securities, net									$ 9,275	$ 653	$ 0
Revenues	$ 652,217	$ 641,427	$ 608,945	$ 677,186	$ 725,966	$ 770,882	$ 715,485	$ 661,615	2,579,775	2,873,948	2,860,849
Total interest expense									99,808	109,339	104,216
Retirement defined benefits expense—other than service costs									3,210	2,806	5,962
Total expenses									2,268,282	2,525,927	2,527,493
Operating income	$ 80,674	$ 99,561	$ 71,556	$ 59,702	$ 100,795	$ 96,655	$ 72,634	$ 77,937	311,493	348,021	333,356
Add back: Retirement defined benefits expense (credit)—other than service costs									3,210	2,806	5,962
Add back: Gain on sale of investment securities, net									9,275	653	0
Income before income taxes									240,624	271,409	254,461
American Savings Bank (ASB)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Interest and dividend income									244,663	266,554	258,225
Noninterest income									78,123	72,778	56,050
Less: Gain on sale of real estate									0	10,762	0
Gain on sale of investment securities, net									9,275	653	0
Revenues									313,511	327,917	314,275
Total interest expense									11,114	18,440	15,539
Provision for credit losses									50,811	23,480	14,745
Noninterest expense									191,590	185,378	177,413
Retirement defined benefits expense—other than service costs									1,813	(472)	1,657
Gain on sale of properties									0	10,762	0
Total expenses									251,702	217,008	206,040
Operating income									61,809	110,909	108,235
Add back: Retirement defined benefits expense (credit)—other than service costs									1,813	(472)	1,657
Add back: Gain on sale of investment securities, net									9,275	653	0
Income before income taxes									$ 69,271	$ 112,034	$ 106,578