Bank segment - Reconciliation of Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Income Statements, Captions [Line Items]
Total revenues	$ 677,186	$ 661,615
Less: Retirement defined benefits gain (expense)—other than service costs	(934)	(763)
Total expenses	617,484	583,678
Operating income	59,702	77,937
Income before income taxes	39,696	58,039
American Savings Bank (ASB)
Condensed Income Statements, Captions [Line Items]
Interest and dividend income	64,975	68,488
Total noninterest income	14,763	14,564
Total revenues	79,738	83,052
Total interest expense	3,900	4,780
Provision for credit losses	10,401	6,870
Noninterest expense	46,468	45,240
Less: Retirement defined benefits gain (expense)—other than service costs	434	(40)
Total expenses	60,335	56,930
Operating income	19,403	26,122
Income before income taxes	$ 18,969	$ 26,162