Bank segment - Income Statement Data (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Noninterest income
Noninterest income	$ 822,044			$ 990,338			$ 2,435,416	$ 2,527,153
Noninterest expense
Income (loss) before income taxes	49,110			79,905			188,781	233,602
Income taxes	7,521			17,352			36,915	48,395
Net income (loss)	41,589			62,553			151,866	185,207
Other comprehensive (loss) income, net of tax benefits	(34,875)	$ (7,609)	$ 20,488	(96,012)	$ (87,840)	$ (117,159)	(21,996)	(301,011)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	6,243			(33,930)			128,453	(117,221)
American Savings Bank (ASB)
Interest and dividend income
Interest and fees on loans	71,540			53,365			204,348	147,499
Interest and dividends on investment securities	14,096			15,052			42,508	43,729
Interest and dividend income	85,636			68,417			246,856	191,228
Interest expense
Interest on deposit liabilities	14,446			1,704			30,944	3,572
Interest on other borrowings	8,598			1,055			25,171	1,199
Total interest expense	23,044			2,759			56,115	4,771
Net interest income	62,592			65,658			190,741	186,457
Provision for credit losses	8,835			(186)			10,053	(692)
Net interest income after provision for credit losses	53,757			65,844			180,688	187,149
Noninterest income
Gain on sale of real estate	0			0			495	1,002
Total noninterest income	15,338			12,994			45,355	41,624
Noninterest expense
Compensation and employee benefits	29,902			28,597			89,500	83,478
Occupancy	5,154			5,577			16,281	16,996
Data processing	5,133			4,509			15,240	13,144
Services	3,627			2,751			8,911	7,712
Equipment	3,125			2,432			8,728	7,163
Office supplies, printing and postage	1,022			1,123			3,296	3,256
Marketing	984			925			2,834	2,877
Other expense	7,399			5,643			19,742	14,542
Noninterest expense	56,346			51,557			164,532	149,168
Income (loss) before income taxes	12,749			27,281			61,511	79,605
Income taxes	1,384			6,525			11,380	17,513
Net income (loss)	11,365			20,756			50,131	62,092
Other comprehensive (loss) income, net of tax benefits	(34,231)			(98,942)			(23,011)	(310,218)
Comprehensive income (loss) attributable to Hawaiian Electric Industries, Inc.	(22,866)			(78,186)			27,120	(248,126)
American Savings Bank (ASB) | Fees from other financial services
Noninterest income
Noninterest income	4,703			4,763			14,391	15,066
American Savings Bank (ASB) | Fee income on deposit liabilities
Noninterest income
Noninterest income	4,924			4,879			14,027	14,122
American Savings Bank (ASB) | Fee income on other financial products
Noninterest income
Noninterest income	2,440			2,416			7,952	7,663
American Savings Bank (ASB) | Bank-owned life insurance
Noninterest income
Noninterest income	2,303			122			5,683	661
American Savings Bank (ASB) | Mortgage banking income
Noninterest income
Noninterest income	341			181			701	1,630
American Savings Bank (ASB) | Other income, net
Noninterest income
Noninterest income	$ 627			$ 633			$ 2,106	$ 1,480