Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Interest income:
Interest and fees on loans	$ 103.9	$ 94.0	$ 292.1	$ 231.6
Interest and dividends on investment securities:
Taxable	13.9	11.7	41.0	30.2
Exempt from federal taxes	0.6	0.8	1.8	2.5
Interest on deposits in banks	2.8	2.3	6.9	4.8
Total interest income	121.2	108.8	341.8	269.1
Interest expense:
Interest on deposits	8.9	6.2	22.3	15.3
Interest on securities sold under repurchase agreements	0.7	0.4	1.8	0.9
Interest on other borrowed funds	0.1	0.4	0.2	0.4
Interest on other debt	0.4	0.2	0.9	1.2
Interest on subordinated debentures held by subsidiary trusts	1.1	0.8	3.0	2.3
Total interest expense	11.2	8.0	28.2	20.1
Net interest income	110.0	100.8	313.6	249.0
Provision for loan losses	2.0	3.4	7.0	7.5
Net interest income after provision for loan losses	108.0	97.4	306.6	241.5
Non-interest income:
Gain (Loss) on Termination of Interest Rate Swap	0.0	(1.1)	0.0	(1.1)
Mortgage banking revenues	6.7	8.2	19.3	22.5
Investment securities gains (losses), net	0.0	0.8	0.0	0.8
Other income	4.5	3.0	11.0	10.9
Total non-interest income	36.2	38.3	109.0	104.6
Non-interest expense:
Salaries and wages	36.8	34.7	105.7	88.4
Employee benefits	11.9	10.2	35.5	29.6
Outsourced technology services	6.8	6.6	20.9	17.9
Occupancy, net	6.5	6.1	18.8	16.0
Furniture and equipment	3.5	3.1	9.5	8.2
OREO expense, net of income	0.2	0.2	0.3	0.2
Professional fees	1.9	1.9	5.2	4.7
FDIC insurance premiums	1.4	1.7	4.3	3.4
Mortgage servicing rights amortization	0.8	0.8	2.3	2.1
Mortgage servicing rights recovery	0.0	0.0	0.0	(0.1)
Core deposit intangibles amortization	2.0	1.9	5.5	3.6
Other expenses	15.8	14.5	48.1	40.9
Acquisition related expenses	3.1	13.0	5.4	23.9
Total non-interest expense	90.7	94.7	261.5	238.8
Income before income tax expense	53.5	41.0	154.1	107.3
Income tax expense	12.1	13.7	34.3	35.0
Net income	$ 41.4	$ 27.3	$ 119.8	$ 72.3
Basic earnings per common share (in dollars per share)	$ 0.71	$ 0.49	$ 2.10	$ 1.46
Diluted earnings per common share (in dollars per share)	$ 0.71	$ 0.48	$ 2.09	$ 1.45
Weighted average common shares outstanding for basic earnings per share computation	58,254,575	56,094,401	56,951,029	49,514,818
Weighted Average Number of Shares Outstanding, Diluted	58,640,475	56,530,868	57,330,027	50,000,882
Credit and Debit Card [Member]
Non-interest income:
Payment services revenues	$ 10.1	$ 12.4	$ 33.5	$ 31.0
Investment Advisory, Management and Administrative Service [Member]
Non-interest income:
Wealth management revenues	5.8	5.5	17.5	15.6
Deposit Account [Member]
Non-interest income:
Payment services revenues	5.7	5.9	16.6	15.3
Financial Service, Other [Member]
Non-interest income:
Payment services revenues	$ 3.4	$ 3.6	$ 11.1	$ 9.6