Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Interest income:
Interest and fees on loans	$ 105.4	$ 112.1	$ 213.2	$ 224.1
Interest and dividends on investment securities:
Taxable	15.8	15.7	31.6	32.9
Exempt from federal taxes	1.4	0.5	2.8	1.0
Interest on deposits in banks	0.7	0.5	1.0	3.0
Total interest income	123.3	128.8	248.6	261.0
Interest expense:
Interest on deposits	2.2	4.5	4.5	11.8
Interest on securities sold under repurchase agreements	0.1	0.1	0.2	0.6
Interest on other debt	1.5	1.0	3.0	1.3
Interest on subordinated debentures held by subsidiary trusts	0.7	0.7	1.4	1.7
Total interest expense	4.5	6.3	9.1	15.4
Net interest income	118.8	122.5	239.5	245.6
(Reversal of) provision for credit losses	0.0	19.5	(5.1)	48.5
Net interest income after provision for (reversal of) credit losses	118.8	103.0	244.6	197.1
Non-interest income:
Investment securities gains (losses), net	(0.1)	0.0	(0.1)	0.0
Mortgage banking revenues	9.6	14.2	21.2	25.1
Other income	2.6	4.3	6.7	7.9
Total non-interest income	35.3	39.7	73.4	78.1
Non-interest expense:
Salaries and wages	41.6	44.2	80.6	84.1
Employee benefits	14.7	10.4	30.8	24.6
Outsourced technology services	8.4	8.3	16.5	16.1
Occupancy, net	7.1	6.8	14.4	14.1
Furniture and equipment	4.1	4.2	8.5	7.0
OREO expense, net of income	0.0	0.1	(0.1)	(0.4)
Professional fees	3.2	3.0	6.6	5.7
FDIC insurance premiums	1.5	1.6	3.1	3.2
Core deposit intangibles amortization	2.5	2.7	5.0	5.6
Other expenses	15.9	14.3	32.0	30.6
Noninterest Expense	99.0	95.6	197.4	190.6
Income before income tax expense	55.1	47.1	120.6	84.6
Income tax expense	12.6	10.4	26.7	18.6
Net income	$ 42.5	$ 36.7	$ 93.9	$ 66.0
Earnings per common share, basic (in dollars per share)	$ 0.69	$ 0.57	$ 1.52	$ 1.02
Earnings per common share, diluted (in dollars per share)	$ 0.69	$ 0.57	$ 1.52	$ 1.02
Weighted average common shares outstanding, basic (in shares)	61,657,593	64,004,455	61,624,917	64,397,320
Weighted average common shares outstanding, diluted (in shares)	61,727,821	64,082,489	61,723,142	64,513,886
Payment services revenues
Non-interest income:
Non-interest income	$ 11.4	$ 9.3	$ 21.6	$ 19.5
Wealth management revenues
Non-interest income:
Wealth management revenues	6.3	5.4	12.6	11.6
Service charges on deposit accounts
Non-interest income:
Non-interest income	3.9	3.6	7.7	9.0
Other service charges, commissions, and fees
Non-interest income:
Non-interest income	$ 1.6	$ 2.9	$ 3.7	$ 5.0