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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Expenses:
Depreciation of property, plant and equipment									$ 200,658	$ 194,273	$ 183,966
Total expenses									2,217,334	2,032,479	2,280,429
Merger termination fee									0	90,000	0
Interest expense, net									91,128	88,558	88,476
Income before income taxes									276,580	373,841	254,788
Income (taxes) benefits									(109,393)	(123,695)	(93,021)
Net income (loss)	$ 32,843	$ 60,544	$ 39,134	$ 34,666	$ 45,107	$ 127,613	$ 44,601	$ 32,825	167,187	250,146	161,767
Hawaiian Electric Industries, Inc.
Revenues
Revenues									798	647	327
Equity in net income of subsidiaries									187,097	199,485	190,033
Expenses:
Operating, administrative and general									17,697	18,701	34,350
Depreciation of property, plant and equipment									548	566	576
Taxes, other than income taxes									496	4,726	440
Total expenses									18,741	23,993	35,366
Income before merger termination fee, interest expense and income (taxes) benefits									169,154	176,139	154,994
Merger termination fee									0	90,000	0
Income before interest expense and income (taxes) benefits									169,154	266,139	154,994
Interest expense, net									9,389	9,037	10,788
Income before income taxes									159,765	257,102	144,206
Income (taxes) benefits									5,532	(8,846)	15,671
Net income (loss)									$ 165,297	$ 248,256	$ 159,877