SCHEDULE I - CONDENSED FINANCIAL INFORMATION OF REGISTRANT - STATEMENTS OF INCOME AND CHANGES IN SHAREHOLDERS' EQUITY (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
Revenues
Revenues									$ 2,614,831		$ 2,380,654
Expenses:
Depreciation of property, plant and equipment									214,036	$ 200,658	194,273
Total expenses									2,527,493	2,209,392	2,024,816
Merger termination fee									0	0	90,000
Retirement defined benefits expense—other than service costs									5,962	7,942	7,663
Interest expense									104,216	91,128	88,558
Income before income taxes									254,461	276,580	373,841
Income (taxes) benefits									(50,797)	(109,393)	(123,695)
Net income (loss)	$ 50,046	$ 66,371	$ 46,527	$ 40,720	$ 32,843	$ 60,544	$ 39,134	$ 34,666	203,664	167,187	250,146
Hawaiian Electric Industries, Inc.
Revenues
Revenues									429	798	647
Equity in net income of subsidiaries									226,972	187,097	199,485
Expenses:
Operating, administrative and general									19,515	16,578	17,515
Depreciation of property, plant and equipment									597	548	566
Taxes, other than income taxes									509	496	4,726
Total expenses									20,621	17,622	22,807
Income before merger termination fee, interest expense and income (taxes) benefits									206,780	170,273	177,325
Merger termination fee									0	0	90,000
Income before interest expense and income (taxes) benefits									206,780	170,273	267,325
Retirement defined benefits expense—other than service costs									674	1,119	1,186
Interest expense									12,664	9,389	9,037
Income before income taxes									193,442	159,765	257,102
Income (taxes) benefits									8,332	5,532	(8,846)
Net income (loss)									$ 201,774	$ 165,297	$ 248,256