Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income
Loans	$ 99,874	$ 91,798	$ 83,371
Federal funds sold and interest bearing deposits	1,330	491	263
Mortgage loans held for sale	191	237	249
Securities
Taxable	8,365	8,451	8,120
Tax-exempt	1,089	1,195	1,167
Total interest income	110,849	102,172	93,170
Interest expense
Deposits	5,975	3,943	3,739
Securities sold under agreements to repurchase and other short term borrowing	316	212	174
Long term debt	955	763	939
Total interest expense	7,246	4,918	4,852
Net interest income	103,603	97,254	88,318
Provision for loan losses	2,550	3,000	750
Net interest income after provision for loan losses	101,053	94,254	87,568
Non-interest income
Wealth management and trust services	20,505	19,155	18,026
Deposit service charges	6,461	6,253	6,010
Debit and credit cards	5,979	5,655	4,876
Treasury management	4,008	3,651	3,404
Mortgage banking	3,221	3,897	3,488
(Loss) on sale of securities available-for-sale	(232)
Investment product sales commissions and fees	2,200	2,145	1,994
Bank owned life insurance	1,159	871	889
Other	1,819	1,910	1,263
Total non-interest income	45,120	43,537	39,950
Non-interest expenses
Compensation	42,584	40,817	36,597
Employee benefits	9,987	8,368	8,112
Net occupancy and equipment	7,393	7,422	6,986
Technology and communication	8,525	7,619	6,891
Marketing and business development	2,716	2,464	2,579
Postage, printing and supplies	1,475	1,521	1,436
Legal and professional	2,393	1,869	1,832
FDIC insurance	960	1,181	1,258
Amortization/impairment of investments in tax credit partnerships	7,124	4,458	634
Capital and deposit based taxes	3,440	2,800	2,413
Other	4,394	3,001	4,660
Total non-interest expenses	90,991	81,520	73,398
Income before income taxes	55,182	56,271	54,120
Income tax expense	17,139	15,244	16,933
Net income	$ 38,043	$ 41,027	$ 37,187
Net income per share, basic (in dollars per share)	$ 1.69	$ 1.84	$ 1.68
Net income per share, diluted (in dollars per share)	$ 1.66	$ 1.80	$ 1.65
Average common shares:
Basic (in shares)	22,532	22,356	22,088
Diluted (in shares)	22,983	22,792	22,459