Bank segment - Income statement data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Noninterest income
Noninterest income	$ 725,111	$ 710,168	$ 1,962,922	$ 1,907,220
Noninterest expense
Income before income taxes	78,693	77,233	189,426	190,091
Income taxes	14,803	10,862	36,390	36,473
Net income	63,890	66,371	153,036	153,618
American Savings Bank (ASB)
Interest and dividend income
Interest and fees on loans	59,260	55,885	175,740	163,318
Interest and dividends on investment securities	7,599	9,300	25,762	27,130
Total interest and dividend income	66,859	65,185	201,502	190,448
Interest expense
Interest on deposit liabilities	4,384	3,635	12,923	9,876
Interest on other borrowings	422	404	1,361	1,293
Total interest expense	4,806	4,039	14,284	11,169
Net interest income	62,053	61,146	187,218	179,279
Provision for loan losses	3,315	6,033	17,873	12,337
Net interest income after provision for loan losses	58,738	55,113	169,345	166,942
Noninterest income
Total noninterest income	16,342	15,311	46,438	42,571
Noninterest expense
Compensation and employee benefits	25,364	23,952	76,626	72,047
Occupancy	5,694	4,363	15,843	12,837
Data processing	3,763	3,583	11,353	10,587
Services	2,829	2,485	7,861	8,560
Equipment	2,163	1,783	6,416	5,385
Office supplies, printing and postage	1,297	1,556	4,320	4,554
Marketing	1,142	993	3,455	2,723
FDIC insurance	(5)	638	1,249	2,078
Other expense	3,676	4,240	12,049	12,897
Total noninterest expense	45,923	43,593	139,172	131,668
Income before income taxes	29,157	26,831	76,611	77,845
Income taxes	6,269	5,610	15,868	17,103
Net income	22,888	21,221	60,743	60,742
American Savings Bank (ASB) | Fees from other financial services
Noninterest income
Noninterest income	5,085	4,543	14,445	13,941
American Savings Bank (ASB) | Fee income on deposit liabilities
Noninterest income
Noninterest income	5,320	5,454	15,402	15,781
American Savings Bank (ASB) | Fee income on other financial products
Noninterest income
Noninterest income	1,706	1,746	5,129	5,075
American Savings Bank (ASB) | Bank-owned life insurance
Noninterest income
Noninterest income	1,660	2,663	6,309	4,667
American Savings Bank (ASB) | Mortgage banking income
Noninterest income
Noninterest income	1,490	169	3,080	1,399
American Savings Bank (ASB) | Gains on sale of investment securities, net
Noninterest income
Noninterest income	653	0	653	0
American Savings Bank (ASB) | Other income, net
Noninterest income
Noninterest income	$ 428	$ 736	$ 1,420	$ 1,708