Bank segment - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Condensed Income Statements, Captions [Line Items]
Less: Gain on sale of investment securities, net	$ 0	$ 9,275	$ 528	$ 9,275
Revenues	680,257	608,945	1,323,203	1,286,131
Provision for credit losses	(12,957)	10,833	(19,992)	20,734
Less: Retirement defined benefits expense (credit)—other than service costs	(1,216)	934	(3,651)	1,868
Total expenses	578,401	537,389	1,123,316	1,154,873
Operating income - Bank	101,856	71,556	199,887	131,258
Income before income taxes	82,944	60,230	163,140	99,926
American Savings Bank (ASB)
Condensed Income Statements, Captions [Line Items]
Interest and dividend income	62,066	59,829	120,686	124,804
Noninterest income	15,194	24,160	34,233	38,923
Less: Gain on sale of investment securities, net	0	9,275	528	9,275
Revenues	77,260	74,714	154,391	154,452
Total interest expense	1,304	3,146	2,793	7,046
Provision for credit losses	(12,207)	15,133	(20,642)	25,534
Noninterest expense	48,171	48,376	95,674	94,844
Less: Retirement defined benefits expense (credit)—other than service costs	(186)	434	(1,464)	868
Total expenses	37,454	66,221	79,289	126,556
Operating income - Bank	39,806	8,493	75,102	27,896
Income before income taxes	$ 39,992	$ 17,334	$ 77,094	$ 36,303