Bank segment (HEI only) - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Revenues	$ 761,650	$ 768,048	$ 685,277	$ 645,874	$ 658,597	$ 673,185	$ 632,281	$ 591,562	$ 2,860,849	$ 2,555,625	$ 2,380,654
Total interest expense									104,216	91,128	88,558
Less: Retirement defined benefits expense—other than service costs									(5,962)	(7,942)	(7,663)
Total expenses									2,527,493	2,209,392	2,024,816
Operating income	$ 84,604	$ 98,064	$ 78,799	$ 71,889	$ 87,220	$ 111,473	$ 77,802	$ 69,738	333,356	346,233	355,838
Add back: Retirement defined benefits expense—other than service costs									5,962	7,942	7,663
Income before income taxes									254,461	276,580	373,841
American Savings Bank (ASB)
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Interest and dividend income									258,225	236,078	218,958
Noninterest income									56,050	61,562	66,966
Revenues									314,275	297,640	285,924
Total interest expense									15,539	12,156	12,755
Provision for loan losses									14,745	10,901	16,763
Noninterest expense									177,413	175,867	169,054
Less: Retirement defined benefits expense—other than service costs									(1,657)	(820)	(875)
Total expenses									206,040	198,104	197,697
Operating income									108,235	99,536	88,227
Add back: Retirement defined benefits expense—other than service costs									1,657	820	875
Income before income taxes									$ 106,578	$ 98,716	$ 87,352