Bank segment - Income statement data (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Noninterest income
Noninterest income	$ 660,421	$ 621,587	$ 1,237,811	$ 1,197,052
Noninterest expense
Income before income taxes	52,694	59,582	110,733	112,858
Income taxes	9,709	13,055	21,587	25,611
Net income	42,985	46,527	89,146	87,247
American Savings Bank (ASB)
Interest and dividend income
Interest and fees on loans	58,620	54,633	116,480	107,433
Interest and dividends on investment securities	7,535	8,628	18,163	17,830
Total interest and dividend income	66,155	63,261	134,643	125,263
Interest expense
Interest on deposit liabilities	4,287	3,284	8,539	6,241
Interest on other borrowings	411	393	939	889
Total interest expense	4,698	3,677	9,478	7,130
Net interest income	61,457	59,584	125,165	118,133
Provision for loan losses	7,688	2,763	14,558	6,304
Net interest income after provision for loan losses	53,769	56,821	110,607	111,829
Noninterest income
Total noninterest income	15,532	13,843	30,096	27,260
Noninterest expense
Compensation and employee benefits	25,750	23,655	51,262	48,095
Occupancy	5,479	4,194	10,149	8,474
Data processing	3,852	3,540	7,590	7,004
Services	2,606	3,028	5,032	6,075
Equipment	2,189	1,874	4,253	3,602
Office supplies, printing and postage	1,663	1,491	3,023	2,998
Marketing	1,323	1,085	2,313	1,730
FDIC insurance	628	727	1,254	1,440
Other expense	4,519	4,556	8,373	8,657
Total noninterest expense	48,009	44,150	93,249	88,075
Income before income taxes	21,292	26,514	47,454	51,014
Income taxes	4,276	5,953	9,599	11,493
Net income	17,016	20,561	37,855	39,521
American Savings Bank (ASB) | Fees from other financial services
Noninterest income
Noninterest income	4,798	4,744	9,360	9,398
American Savings Bank (ASB) | Fee income on deposit liabilities
Noninterest income
Noninterest income	5,004	5,138	10,082	10,327
American Savings Bank (ASB) | Fee income on other financial products
Noninterest income
Noninterest income	1,830	1,675	3,423	3,329
American Savings Bank (ASB) | Bank-owned life insurance
Noninterest income
Noninterest income	2,390	1,133	4,649	2,004
American Savings Bank (ASB) | Mortgage banking income
Noninterest income
Noninterest income	976	617	1,590	1,230
American Savings Bank (ASB) | Other income, net
Noninterest income
Noninterest income	$ 534	$ 536	$ 992	$ 972