Quarterly information (unaudited) (Details) - USD ($) $ / shares in Units, $ 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
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 652,217	$ 641,427	$ 608,945	$ 677,186	$ 725,966	$ 770,882	$ 715,485	$ 661,615	$ 2,579,775	$ 2,873,948	$ 2,860,849
Operating income	80,674	99,561	71,556	59,702	100,795	96,655	72,634	77,937	311,493	348,021	333,356
Net income	50,958	65,503	49,360	33,893	66,736	63,890	42,985	46,161	199,714	219,772	203,664
Net income for common stock	$ 50,485	$ 65,032	$ 48,887	$ 33,420	$ 66,263	$ 63,419	$ 42,512	$ 45,688	$ 197,824	$ 217,882	$ 201,774
Basic earnings per common share (in dollars per share)	$ 0.46	$ 0.60	$ 0.45	$ 0.31	$ 0.61	$ 0.58	$ 0.39	$ 0.42	$ 1.81	$ 2.00	$ 1.85
Diluted earnings per common share (in dollars per share)	0.46	0.59	0.45	0.31	0.61	0.58	0.39	0.42	1.81	1.99	1.85
Dividends declared per common share (in dollars per share)	$ 0.33	$ 0.33	$ 0.33	$ 0.33	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 1.32	$ 1.28	$ 1.24
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 571,095	$ 562,568	$ 534,215	$ 597,442	$ 645,333	$ 688,330	$ 633,784	$ 578,495	$ 2,265,320	$ 2,545,942	$ 2,546,525
Operating income	68,273	88,518	67,801	43,958	70,331	71,793	55,694	56,560	268,550	254,378	241,661
Net income	43,540	60,563	42,828	24,404	45,860	47,277	33,073	32,625	171,335	158,835	145,648
Net income for common stock	$ 43,041	$ 60,065	$ 42,329	$ 23,905	45,361	$ 46,779	$ 32,574	$ 32,126	$ 169,340	$ 156,840	$ 143,653
ASB Hawaii, Inc.
Condensed Financial Statements, Captions [Line Items]
Gain on sale of properties					10,800
Gain on sale of properties included in net income					$ 7,900
Gain on the sale of properties, earnings per share basic and diluted (in dollars per share)					$ 0.07
Statutory income tax rate					26.80%