Consolidated Statements of Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest income:
Interest and fees on loans	$ 979.7	$ 790.2	$ 430.2
Interest and dividends on investment securities:
Taxable	269.1	213.9	68.6
Exempt from federal taxes	3.2	3.9	4.1
Interest on deposits in banks	15.7	8.7	2.6
Total interest income	1,280.1	1,021.5	506.5
Interest expense:
Interest on deposits	242.6	48.3	8.1
Interest on securities sold under repurchase agreements	6.4	2.5	0.4
Interest on other borrowed funds	133.8	15.3	0.0
Interest on long-term debt	5.8	6.0	6.0
Interest on subordinated debentures held by subsidiary trusts	12.7	6.8	2.8
Total interest expense	401.3	78.9	17.3
Net interest income	878.8	942.6	489.2
Provision for (reversal of) credit losses	32.2	82.7	(14.6)
Net interest income after provision for (reversal of) credit losses	846.6	859.9	503.8
Payment Services Revenues	76.4	74.1	45.1
Non-interest income:
Revenue from Contract with Customer, Excluding Assessed Tax	9.5	15.5	7.9
Fees and Commissions, Mortgage Banking and Servicing	8.4	18.7	40.8
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions	35.3	34.3	26.3
Service Charges on Deposit Accounts	23.0	24.6	16.5
Investment securities (losses) gains, net	(23.5)	(24.4)	1.1
Other income	17.9	20.4	11.8
Total non-interest income	147.0	163.2	149.5
Non-interest expense:
Salaries and wages	263.1	282.1	164.9
Employee benefits	75.3	77.5	55.8
Information Technology and Data Processing	59.0	54.3	32.8
Occupancy, Net	48.0	44.0	28.7
Equipment Expense	22.1	23.4	17.6
OREO expense, net of income	1.5	2.3	(0.2)
Professional fees	19.1	19.1	12.1
FDIC insurance premiums	31.5	14.0	6.6
Other intangibles amortization	15.7	15.9	9.9
Other expenses	121.5	114.5	65.7
Acquisition related expenses	0.0	118.9	11.6
Total non-interest expense	656.8	766.0	405.5
Income before income tax	336.8	257.1	247.8
Provision for income tax	79.3	54.9	55.7
Net income	$ 257.5	$ 202.2	$ 192.1
Basic earnings per common share (in dollars per share)	$ 2.48	$ 1.96	$ 3.12
Diluted earnings per common share (in dollars per share)	$ 2.48	$ 1.96	$ 3.11
Other Interest and Dividend Income	$ 12.4	$ 4.8	$ 1.0