Quarterly information (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 725,966	$ 771,535	$ 715,485	$ 661,615	$ 761,650	$ 768,048	$ 685,277	$ 645,874	$ 2,874,601	$ 2,860,849	$ 2,555,625
Operating income	100,795	97,308	72,634	77,937	84,604	98,064	78,799	71,889	348,674	333,356	346,233
Net income	66,736	63,890	42,985	46,161	50,046	66,371	46,527	40,720	219,772	203,664	167,187
Net income for common stock	$ 66,263	$ 63,419	$ 42,512	$ 45,688	$ 49,573	$ 65,900	$ 46,054	$ 40,247	$ 217,882	$ 201,774	$ 165,297
Basic earnings per common share (in dollars per share)	$ 0.61	$ 0.58	$ 0.39	$ 0.42	$ 0.46	$ 0.61	$ 0.42	$ 0.37	$ 2.00	$ 1.85	$ 1.52
Diluted earnings per common share (in dollars per share)	0.61	0.58	0.39	0.42	0.45	0.60	0.42	0.37	1.99	1.85	1.52
Dividends declared per common share (in dollars per share)	$ 0.32	$ 0.32	$ 0.32	$ 0.32	$ 0.31	$ 0.31	$ 0.31	$ 0.31	$ 1.28	$ 1.24	$ 1.24
Hawaiian Electric Company, Inc. and Subsidiaries
Condensed Financial Statements, Captions [Line Items]
Revenues	$ 645,333	$ 688,330	$ 633,784	$ 578,495	$ 680,563	$ 687,409	$ 608,126	$ 570,427	$ 2,545,942	$ 2,546,525	$ 2,257,566
Operating income	70,331	71,793	55,694	56,560	61,112	74,036	55,144	51,369	254,378	241,661	263,524
Net income	45,860	47,277	33,073	32,625	35,796	50,210	31,668	27,974	158,835	145,648	121,946
Net income for common stock	45,361	$ 46,779	$ 32,574	$ 32,126	$ 35,297	$ 49,712	$ 31,169	$ 27,475	$ 156,840	$ 143,653	$ 119,951
ASB Hawaii, Inc.
Condensed Financial Statements, Captions [Line Items]
Gain on sale of properties	10,800
Gain on the 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%