Bank segment - Reconciliation of income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Condensed Income Statements, Captions [Line Items]
Less: Gain on sale of investment securities, net	$ 8,123	$ 528
Revenues	785,068	642,946
Provision for credit losses	(3,763)	(7,035)
Less: Retirement defined benefits credit—other than service costs	(1,243)	(2,435)
Total expenses	685,792	544,915
Operating income - Bank	99,276	98,031
Income before income taxes	87,480	80,196
American Savings Bank (ASB)
Condensed Income Statements, Captions [Line Items]
Interest and dividend income	59,989	58,620
Noninterest income	16,128	19,039
Less: Gain on sale of real estate	1,002	0
Less: Gain on sale of investment securities, net	0	528
Revenues	75,115	77,131
Total interest expense	952	1,489
Provision for credit losses	(3,263)	(8,435)
Noninterest expense	48,213	47,503
Less: Retirement defined benefits credit—other than service costs	(185)	(1,278)
Total expenses	45,085	41,835
Operating income - Bank	30,030	35,296
Income before income taxes	$ 30,215	$ 37,102