Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest income:
Interest and fees on loans	$ 107.8	$ 112.0
Interest and dividends on investment securities:
Taxable	15.8	17.2
Exempt from federal taxes	1.4	0.5
Interest on deposits in banks	0.3	2.5
Total interest income	125.3	132.2
Interest expense:
Interest on deposits	2.3	7.3
Interest on securities sold under repurchase agreements	0.1	0.5
Interest on other debt	1.5	0.3
Interest on subordinated debentures held by subsidiary trusts	0.7	1.0
Total interest expense	4.6	9.1
Net interest income	120.7	123.1
(Reversal of) provision for credit losses	(5.1)	29.0
Net interest income after provision for (reversal of) credit losses	125.8	94.1
Non-interest income:
Gain (Loss) on Sale of Other Investments	0.0	0.0
Mortgage banking revenues	11.6	10.9
Other income	4.1	3.6
Total non-interest income	38.1	38.4
Non-interest expense:
Salaries and wages	39.0	39.9
Employee benefits	16.1	14.2
Outsourced technology services	8.1	7.8
Occupancy, net	7.3	7.3
Furniture and equipment	4.4	2.8
OREO expense, net of income	(0.1)	(0.5)
Professional fees	3.4	2.7
FDIC insurance premiums	1.6	1.6
Core deposit intangibles amortization	2.5	2.9
Other expenses	16.1	16.3
Noninterest Expense	98.4	95.0
Income before income tax expense	65.5	37.5
Income tax expense	14.1	8.2
Net income	$ 51.4	$ 29.3
Earnings per common share, basic (in dollars per share)	$ 0.83	$ 0.45
Earnings per common share, diluted (in dollars per share)	$ 0.83	$ 0.45
Weighted average common shares outstanding, basic (in shares)	61,591,877	64,790,186
Weighted average common shares outstanding, diluted (in shares)	61,714,063	64,937,107
Payment services revenues
Non-interest income:
Non-interest income	$ 10.2	$ 10.2
Wealth management revenues
Non-interest income:
Wealth management revenues	6.3	6.2
Service charges on deposit accounts
Non-interest income:
Non-interest income	3.8	5.4
Other service charges, commissions, and fees
Non-interest income:
Non-interest income	$ 2.1	$ 2.1