Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Interest income:
Interest and fees on loans	$ 1,022.2	$ 979.7	$ 790.2
Interest and dividends on investment securities:
Taxable	243.5	269.1	213.9
Exempt from federal taxes	2.8	3.2	3.9
Interest on deposits in banks	22.2	15.7	8.7
Total interest income	1,302.5	1,280.1	1,021.5
Interest expense:
Interest on deposits	325.9	242.6	48.3
Interest on securities sold under repurchase agreements	6.7	6.4	2.5
Interest on other borrowed funds	123.4	133.8	15.3
Interest on long-term debt	11.8	5.8	6.0
Interest on subordinated debentures held by subsidiary trusts	13.1	12.7	6.8
Total interest expense	480.9	401.3	78.9
Net interest income	821.6	878.8	942.6
Provision for credit losses	67.8	32.2	82.7
Net interest income after provision for credit losses	753.8	846.6	859.9
Payment Services Revenues	73.6	76.4	74.1
Noninterest income:
Revenue from Contract with Customer, Excluding Assessed Tax	9.0	9.5	15.5
Fees and Commissions, Mortgage Banking and Servicing	6.6	8.4	18.7
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions	38.8	35.3	34.3
Service Charges on Deposit Accounts	25.7	23.0	24.6
Investment securities losses, net	0.0	(23.5)	(24.4)
Other income	24.4	17.9	20.4
Total noninterest income	178.1	147.0	163.2
Noninterest expense:
Salaries and wages	270.9	263.1	282.1
Employee benefits	76.4	75.3	77.5
Information Technology and Data Processing	56.2	59.0	54.3
Occupancy, Net	48.7	48.0	44.0
Equipment Expense	20.7	22.1	23.4
OREO expense, net	4.1	1.5	2.3
Professional fees	21.6	19.1	19.1
FDIC insurance premiums	24.0	31.5	14.0
Other intangibles amortization	14.6	15.7	15.9
Other expenses	100.2	121.5	114.5
Acquisition related expenses	0.0	0.0	118.9
Total noninterest expense	637.4	656.8	766.0
Income before income tax	294.5	336.8	257.1
Provision for income tax	68.5	79.3	54.9
Net income	$ 226.0	$ 257.5	$ 202.2
Basic earnings per common share (in dollars per share)	$ 2.19	$ 2.48	$ 1.96
Diluted earnings per common share (in dollars per share)	$ 2.19	$ 2.48	$ 1.96
Other Interest and Dividend Income	$ 11.8	$ 12.4	$ 4.8