Bank segment (HEI only) - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Revenues	$ 725,966	$ 771,535	$ 715,485	$ 661,615	$ 761,650	$ 768,048	$ 685,277	$ 645,874	$ 2,874,601	$ 2,860,849	$ 2,555,625
Total interest expense									109,339	104,216	91,128
Less: Retirement defined benefits credit (expense)—other than service costs									(2,806)	(5,962)	(7,942)
Total expenses									2,525,927	2,527,493	2,209,392
Operating income	$ 100,795	$ 97,308	$ 72,634	$ 77,937	$ 84,604	$ 98,064	$ 78,799	$ 71,889	348,674	333,356	346,233
Add back: Retirement defined benefits expense (credit)—other than service costs									2,806	5,962	7,942
Income before income taxes									271,409	254,461	276,580
American Savings Bank (ASB)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Interest and dividend income									266,554	258,225	236,078
Noninterest income									72,778	56,050	61,562
Less: Gain on sale of real estate									(10,762)	0	0
Revenues									328,570	314,275	297,640
Total interest expense									18,440	15,539	12,156
Provision for loan losses									23,480	14,745	10,901
Noninterest expense									185,378	177,413	175,867
Less: Retirement defined benefits credit (expense)—other than service costs									472	(1,657)	(820)
Add: Gain on sale of real estate									(10,762)	0	0
Total expenses									217,008	206,040	198,104
Operating income									111,562	108,235	99,536
Add back: Retirement defined benefits expense (credit)—other than service costs									(472)	1,657	820
Income before income taxes									$ 112,034	$ 106,578	$ 98,716