Bank segment - Income statement data (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest expense
Provision for credit losses	$ (8,435)	$ 10,401
Noninterest income
Noninterest income	541,300	618,605
Noninterest expense
Income before income taxes	80,196	39,696
Income taxes	15,365	5,803
Other comprehensive income (loss), net of tax (benefits)	(44,016)	18,212
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	20,342	51,632
American Savings Bank (ASB)
Interest and dividend income
Interest and fees on loans	49,947	55,545
Interest and dividends on investment securities	8,673	9,430
Total interest and dividend income	58,620	64,975
Interest expense
Interest on deposit liabilities	1,462	3,587
Interest on other borrowings	27	313
Total interest expense	1,489	3,900
Net interest income	57,131	61,075
Provision for credit losses	(8,435)	10,401
Net interest income after provision for credit losses	65,566	50,674
Noninterest income
Total noninterest income	19,039	14,763
Noninterest expense
Compensation and employee benefits	28,037	25,777
Occupancy	4,969	5,267
Data processing	4,351	3,837
Services	2,862	2,809
Equipment	2,222	2,339
Office supplies, printing and postage	1,044	1,341
Marketing	648	802
FDIC insurance	816	102
Other expense	2,554	4,194
Total noninterest expense	47,503	46,468
Income before income taxes	37,102	18,969
Income taxes	7,546	3,208
Net income attributable to Hawaiian Electric	29,556	15,761
Other comprehensive income (loss), net of tax (benefits)	(45,754)	19,847
Comprehensive income attributable to Hawaiian Electric Industries, Inc.	(16,198)	35,608
American Savings Bank (ASB) | Fees from other financial services
Noninterest income
Noninterest income	5,073	4,571
American Savings Bank (ASB) | Fee income on deposit liabilities
Noninterest income
Noninterest income	3,863	5,113
American Savings Bank (ASB) | Fee income on other financial products
Noninterest income
Noninterest income	2,442	1,872
American Savings Bank (ASB) | Bank-owned life insurance
Noninterest income
Noninterest income	2,561	794
American Savings Bank (ASB) | Mortgage banking income
Noninterest income
Noninterest income	4,300	2,000
American Savings Bank (ASB) | Gain on sale of investment securities, net
Noninterest income
Noninterest income	528	0
American Savings Bank (ASB) | Other income, net
Noninterest income
Noninterest income	$ 272	$ 413