Consolidated Statements of Income - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Interest and fees on loans	$ 253,131,000	$ 224,244,000	$ 214,724,000
Interest Income, Securities, Operating, Taxable	22,465,000	20,851,000	20,120,000
Nontaxable interest and dividends on securities	88,000	117,000	127,000
Interest on loans held for sale	92,000	235,000	225,000
Interest on federal funds sold and short-term investments	1,418,000	1,190,000	349,000
Total interest and dividend income	277,194,000	246,637,000	235,545,000
Interest expense
Interest on deposits	12,702,000	11,140,000	11,576,000
Interest on borrowings	5,632,000	7,653,000	9,041,000
Total interest expense	18,334,000	18,793,000	20,617,000
Net interest income	258,860,000	227,844,000	214,928,000
Provision (benefit)	2,950,000	6,075,000	1,500,000
Net interest income after provision for loan losses	255,910,000	221,769,000	213,428,000
Noninterest income
Deposit account fees	17,822,000	18,652,000	18,560,000
Interchange and ATM fees	17,291,000	16,210,000	14,728,000
Investment management	23,802,000	21,809,000	20,735,000
Fees and Commission Mortgage Banking	4,960,000	6,607,000	5,163,000
Increase in cash surrender value of life insurance policies	4,127,000	4,089,000	3,692,000
Available-For-Sale Securities - Fixed Income Gross Realized Gains	0	0	798,000
Gain (Loss) on Sale of Equity Investments	19,000	6,000	20,000
Loan level derivative income	3,836,000	6,155,000	3,830,000
Other noninterest income	11,137,000	8,900,000	8,362,000
Total noninterest income	82,994,000	82,428,000	75,888,000
Noninterest expenses
Salaries and employee benefits	116,600,000	108,636,000	105,068,000
Occupancy and equipment expenses	24,693,000	22,867,000	23,020,000
Data processing & facilities management	4,988,000	4,975,000	4,631,000
FDIC assessment	3,068,000	3,380,000	3,979,000
Advertising expense	4,989,000	5,202,000	4,645,000
Consulting expense	4,038,000	3,486,000	3,680,000
Debit Card Expense	3,430,000	2,993,000	2,456,000
Gains (Losses) on Extinguishment of Debt	0	437,000	122,000
Available-for-Sale Securities - Fixed Income Gross Realized Losses	0	0	1,124,000
Available-For-Sale Securities - Equity Gross Realized Losses	16,000	32,000	99,000
Merger and acquisition expense	3,393,000	5,455,000	10,501,000
Software Maintenance	3,636,000	3,061,000	2,759,000
Other noninterest expenses	35,508,000	31,598,000	35,054,000
Total noninterest expenses	204,359,000	192,122,000	197,138,000
Income before income taxes	134,545,000	112,075,000	92,178,000
Provision for income taxes	47,341,000	35,427,000	27,218,000
Net Income	$ 87,204,000	$ 76,648,000	$ 64,960,000
Basic earnings per share (in dollars per share)	$ 3.19	$ 2.90	$ 2.51
Diluted earnings per share (in dollars per share)	$ 3.19	$ 2.90	$ 2.50
Weighted average common shares (basic) (in shares)	27,294,028	26,404,071	25,891,382
Common share equivalents (in shares)	78,076	51,847	68,566
Weighted average common shares (diluted) (in shares)	27,372,104	26,455,918	25,959,948
Retained Earnings
Noninterest expenses
Net Income	$ 87,204,000	$ 76,648,000	$ 64,960,000
Cash dividends declared (in dollars per share)	$ 1.28	$ 1.16	$ 1.04