Bank segment - Reconciliation of income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Condensed Income Statements, Captions [Line Items]
Less: Gain on sale of investment securities, net	$ 0	$ 0	$ 8,123	$ 528
Revenues	895,607	680,257	1,680,675	1,323,203
Less: Retirement defined benefits credit—other than service costs	(1,246)	(1,216)	(2,489)	(3,651)
Total expenses	808,939	578,401	1,494,731	1,123,316
Operating income - bank	86,668	101,856	185,944	199,887
Income before income taxes	66,217	82,944	153,697	163,140
American Savings Bank (ASB)
Condensed Income Statements, Captions [Line Items]
Interest and dividend income	62,822	62,066	122,811	120,686
Noninterest income	12,502	15,194	28,630	34,233
Less: Gain on sale of real estate	0	0	1,002	0
Less: Gain on sale of investment securities, net	0	0	0	528
Revenues	75,324	77,260	150,439	154,391
Total interest expense	1,060	1,304	2,012	2,793
Provision for credit losses	2,757	(12,207)	(506)	(20,642)
Noninterest expense	49,398	48,171	97,611	95,674
Less: Retirement defined benefits credit—other than service costs	(186)	(186)	(371)	(1,464)
Total expenses	53,401	37,454	98,486	79,289
Operating income - bank	21,923	39,806	51,953	75,102
Income before income taxes	$ 22,109	$ 39,992	$ 52,324	$ 77,094