SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS 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
Revenues
Revenues									$ 2,269,451	$ 2,622,025
Expenses:
Depreciation of property, plant and equipment									238,114	229,858	$ 214,036
Total expenses									2,268,282	2,525,927	2,527,493
Retirement defined benefits expense—other than service costs									3,210	2,806	5,962
Interest expense									99,808	109,339	104,216
Income before income taxes									240,624	271,409	254,461
Income tax benefits									(40,910)	(51,637)	(50,797)
Net income (loss)	$ 50,958	$ 65,503	$ 49,360	$ 33,893	$ 66,736	$ 63,890	$ 42,985	$ 46,161	199,714	219,772	203,664
Hawaiian Electric (parent only)
Revenues
Revenues									208	777	429
Equity in net income of subsidiaries									227,098	246,005	226,972
Expenses:
Operating, administrative and general									20,731	19,195	19,515
Depreciation of property, plant and equipment									485	570	597
Taxes, other than income taxes									654	570	509
Total expenses									21,870	20,335	20,621
Income before interest expense and income tax benefits									205,436	226,447	206,780
Retirement defined benefits expense—other than service costs									634	442	674
Interest expense									18,237	17,930	12,664
Income before income taxes									186,565	208,075	193,442
Income tax benefits									11,259	9,807	8,332
Net income (loss)									$ 197,824	$ 217,882	$ 201,774