Bank segment - Income statement data (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Noninterest expense
Income before income taxes	$ 95,139	$ 179,205	$ 206,347	$ 301,242
Income taxes	34,595	51,592	72,003	96,203
Net income	60,544	127,613	134,344	205,039
American Savings Bank (ASB)
Interest and dividend income
Interest and fees on loans	52,210	50,444	155,269	148,571
Interest and dividends on investment securities	6,850	4,759	20,593	14,219
Total interest and dividend income	59,060	55,203	175,862	162,790
Interest expense
Interest on deposit liabilities	2,444	1,871	6,858	5,154
Interest on other borrowings	470	1,464	2,110	4,416
Total interest expense	2,914	3,335	8,968	9,570
Net interest income	56,146	51,868	166,894	153,220
Provision for loan losses	490	5,747	7,231	15,266
Net interest income after provision for loan losses	55,656	46,121	159,663	137,954
Noninterest income
Fees from other financial services	5,635	5,599	17,055	16,799
Fee income on deposit liabilities	5,533	5,627	16,526	16,045
Fee income on other financial products	1,904	2,151	5,741	6,563
Bank-owned life insurance	1,257	1,616	4,165	3,620
Mortgage banking income	520	2,347	1,896	5,096
Gains on sale of investment securities, net	0	0	0	598
Other income, net	380	1,165	1,229	1,786
Total noninterest income	15,229	18,505	46,612	50,507
Noninterest expense
Compensation and employee benefits	23,724	22,844	71,703	67,197
Occupancy	4,284	3,991	12,623	12,244
Data processing	3,262	3,150	9,749	9,599
Services	2,863	2,427	7,989	8,093
Equipment	1,814	1,759	5,333	5,193
Office supplies, printing and postage	1,444	1,483	4,506	4,431
Marketing	934	747	2,290	2,507
FDIC insurance	746	907	2,296	2,704
Other expense	5,050	4,591	14,066	13,948
Total noninterest expense	44,121	41,899	130,555	125,916
Income before income taxes	26,764	22,727	75,720	62,545
Income taxes	9,172	7,623	25,582	21,483
Net income	$ 17,592	$ 15,104	$ 50,138	$ 41,062