Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
INTEREST INCOME
Loans, including fees	$ 222,022	$ 204,467	$ 190,292
Securities:
Taxable	7,171	5,229	5,492
Tax-exempt	737	964	982
Federal funds sold	61	1	14
Interest-bearing deposits with banks	18,077	7,908	4,265
Total interest income	248,068	218,569	201,045
INTEREST EXPENSE
Deposits	18,790	12,638	10,251
Short-term borrowings	17	7	4
Long-term borrowings			32
Junior subordinated debentures	2,122	2,096	1,966
Total interest expense	20,929	14,741	12,253
Net interest income	227,139	203,828	188,792
Provision for loan losses	8,512	11,519	7,675
Net interest income after provision for loan losses	218,627	192,309	181,117
NONINTEREST INCOME
Trust revenue	12,002	10,630	9,091
Service charges on deposits	65,552	62,233	57,651
Securities transactions (includes accumulated other comprehensive income reclassifications of $17, $15 and $3,814, respectively)	4,060	(59)	9,269
Income from sales of loans	2,921	2,825	1,968
Insurance commissions	16,811	15,559	14,791
Cash management	11,155	10,616	7,510
(Loss) gain on sale of other assets	(60)	46	79
Other	5,629	5,182	5,449
Total noninterest income	118,070	107,032	105,808
NONINTEREST EXPENSE
Salaries and employee benefits	125,149	119,662	113,083
Occupancy, net	12,591	12,313	11,512
Depreciation	9,603	10,114	9,966
Amortization of intangible assets	2,188	2,269	1,935
Data processing services	4,654	4,796	4,579
Net expense (income) from other real estate owned	421	(747)	324
Marketing and business promotion	7,389	7,236	6,986
Deposit insurance	2,261	2,904	3,358
Other	36,136	32,857	33,972
Total noninterest expense	200,392	191,404	185,715
Income before taxes	136,305	107,937	101,210
Income tax expense	49,866	37,263	35,040
Net income	$ 86,439	$ 70,674	$ 66,170
NET INCOME PER COMMON SHARE
Basic	$ 2.72	$ 2.27	$ 2.13
Diluted	$ 2.65	$ 2.22	$ 2.09
OTHER COMPREHENSIVE INCOME
Unrealized losses on securities, net of tax of $861, $897 and $207, respectively	$ (2,431)	$ (1,424)	$ (327)
Reclassification adjustment for gains included in net income, net of tax of $(7), $6 and $1,475, respectively	10	(9)	(2,339)
Other comprehensive loss, net of tax of $854, $903 and $1,682, respectively	(2,421)	(1,433)	(2,666)
Comprehensive income	$ 84,018	$ 69,241	$ 63,504