CONDENSED CONSOLIDATED STATEMENTS OF INCOME - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Income:
Interest and fees on loans	$ 172,091,000	$ 150,868,000	$ 135,170,000
Interest on loans held for sale	279,000	387,000	544,000
Interest on deposits with banks	410,000	213,000	98,000
Interest and dividends on investment securities:
Taxable	13,881,000	11,500,000	14,440,000
Exempt from federal income taxes	8,111,000	7,583,000	8,059,000
Interest on federal funds sold	27,000	5,000	1,000
Total interest income	194,799,000	170,556,000	158,312,000
Interest Expense:
Interest on deposits	13,256,000	8,161,000	5,878,000
Interest on retail repurchase agreements and federal funds purchased	337,000	290,000	255,000
Interest on advances from FHLB	12,426,000	11,610,000	13,081,000
Interest on subordinated debt	12,000	943,000	899,000
Total interest expense	26,031,000	21,004,000	20,113,000
Net interest income	168,768,000	149,552,000	138,199,000
Provision for loan losses	2,977,000	5,546,000	5,371,000
Net interest income after provision for loan losses	165,791,000	144,006,000	132,828,000
Non-interest Income:
Investment securities gains	1,273,000	1,932,000	36,000
Service charges on deposit accounts	8,298,000	7,953,000	7,607,000
Mortgage banking activities	2,734,000	4,049,000	3,114,000
Wealth management income	19,146,000	17,805,000	19,931,000
Insurance agency commissions	6,231,000	5,408,000	5,176,000
Income from bank owned life insurance	2,403,000	2,462,000	2,571,000
Bank card fees	4,827,000	4,674,000	4,652,000
Other income	6,331,000	6,759,000	6,814,000
Total non-interest income	51,243,000	51,042,000	49,901,000
Non-interest Expenses:
Salaries and employee benefits	73,132,000	71,354,000	71,003,000
Occupancy expense of premises	13,053,000	12,960,000	12,809,000
Equipment expenses	7,015,000	6,883,000	6,071,000
Marketing	3,119,000	2,851,000	2,896,000
Outside data services	5,486,000	5,377,000	5,023,000
FDIC insurance	3,305,000	2,741,000	2,491,000
Amortization of intangible assets	101,000	130,000	372,000
Litigation expense	0	0	(3,869,000)
Merger expenses	4,252,000	0	0
Other Expense	19,636,000	20,762,000	18,551,000
Total non-interest expenses	129,099,000	123,058,000	115,347,000
Income before income taxes	87,935,000	71,990,000	67,382,000
Income tax expense	34,726,000	23,740,000	22,027,000
Net income	$ 53,209,000	$ 48,250,000	$ 45,355,000
Per share information:
Basic net income per share	$ 2.2	$ 2	$ 1.84
Diluted net income per share	2.2	2	1.84
Dividends declared per common share	$ 1.04	$ 0.98	$ 0.9