Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Interest and fees on loans	$ 324,769	$ 259,219	$ 246,015
Interest and dividends on investment securities:
Taxable	42,697	32,160	30,861
Exempt from federal taxes	3,156	3,447	3,998
Interest on deposits in banks	7,146	2,589	1,537
Interest on federal funds sold	9	11	12
Total interest income	377,777	297,426	282,423
Interest expense:
Interest on deposits	21,367	12,662	13,107
Interest on securities sold under repurchase agreements	1,253	429	231
Interest on other borrowed funds	1,537	0	0
Interest on long-term debt	599	1,815	2,300
Interest on subordinated debentures held by subsidiary trusts	3,178	2,755	2,422
Total interest expense	27,934	17,661	18,060
Net interest income	349,843	279,765	264,363
Provision for loan losses	11,053	9,991	6,822
Net interest income after provision for loan losses	338,790	269,774	257,541
Non-interest income:
Payment services revenues	43,308	34,374	32,750
Mortgage banking revenues	28,896	37,222	29,973
Wealth management revenues	21,067	20,460	19,907
Service charges on deposit accounts	21,276	18,426	17,031
Other service charges, commissions and fees	13,358	11,506	10,404
Loss on termination of interest rate swap	(1,132)	0	0
Investment securities gains, net	718	330	137
Other income	14,262	10,028	11,313
Non-recurring litigation recovery	0	4,150	0
Total non-interest income	141,753	136,496	121,515
Non-interest expense:
Salaries and wages	122,751	108,684	101,451
Employee benefits	37,561	35,193	31,324
Occupancy, net	22,410	17,714	17,879
Furniture and equipment	11,467	9,584	15,524
Outsourced technology services	25,087	20,547	10,124
FDIC insurance premiums	4,605	4,548	4,858
Professional fees	6,847	4,990	6,458
OREO expense, net of income	467	(44)	(1,475)
Mortgage servicing rights amortization	3,038	2,957	2,434
Mortgage servicing rights impairment recovery	(93)	(35)	(97)
Core deposit intangibles amortization	5,438	3,427	3,388
Other expenses	57,087	50,625	50,936
Loss contingency expense	0	0	5,000
Acquisition related expenses	27,156	2,821	795
Total non-interest expense	323,821	261,011	248,599
Income before income tax expense	156,722	145,259	130,457
Income tax expense	50,201	49,623	43,662
Net income	$ 106,521	$ 95,636	$ 86,795
Basic earnings per common share (in dollars per share)	$ 2.07	$ 2.15	$ 1.92
Diluted earnings per common share (in dollars per share)	$ 2.05	$ 2.13	$ 1.90