Reportable Operating Segments - Selected Business Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Selected business segment financial information
Net interest income (expense)	$ 133,872	$ 129,158
Benefit (Provision) for credit losses	5,747
Net interest income after provision for credit losses	139,619	129,158
Noninterest income	41,380	43,868
Noninterest expense	(104,042)	(96,306)
Income before provision for income taxes	76,957	76,720
Benefit (provision) for income taxes	(19,238)	(19,027)
Net income	57,719	57,693
Total assets	25,042,720		$ 24,992,410
Retail Banking
Selected business segment financial information
Net interest income (expense)	94,048	94,454
Benefit (Provision) for credit losses	1,841	1,470
Net interest income after provision for credit losses	95,889	95,924
Noninterest income	23,315	23,575
Noninterest expense	(70,220)	(62,889)
Income before provision for income taxes	48,984	56,610
Benefit (provision) for income taxes	(12,150)	(14,126)
Net income	36,834	42,484
Commercial Banking
Selected business segment financial information
Net interest income (expense)	35,088	38,266
Benefit (Provision) for credit losses	2,542	2,030
Net interest income after provision for credit losses	37,630	40,296
Noninterest income	18,655	16,041
Noninterest expense	(26,505)	(22,478)
Income before provision for income taxes	29,780	33,859
Benefit (provision) for income taxes	(7,253)	(8,344)
Net income	22,527	25,515
Treasury and Other
Selected business segment financial information
Net interest income (expense)	4,736	(3,562)
Benefit (Provision) for credit losses	1,364	(3,500)
Net interest income after provision for credit losses	6,100	(7,062)
Noninterest income	(590)	4,252
Noninterest expense	(7,317)	(10,939)
Income before provision for income taxes	(1,807)	(13,749)
Benefit (provision) for income taxes	165	3,443
Net income	$ (1,642)	$ (10,306)