Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest income
Loans		$ 118,467	$ 99,924	$ 91,833
Federal funds sold and interest bearing deposits		1,307	1,330	491
Mortgage loans held for sale		166	191	237
Securities
Taxable		9,001	8,365	8,451
Tax-exempt		832	1,089	1,195
Total interest income		129,773	110,899	102,207
Interest expense
Deposits		13,441	5,975	3,943
Securities sold under agreements to repurchase and other short term borrowing		992	316	212
Long term debt		924	955	763
Total interest expense		15,357	7,246	4,918
Net interest income		114,416	103,653	97,289
Provision for loan losses		2,705	2,550	3,000
Net interest income after provision for loan losses		111,711	101,103	94,289
Non-interest income:
Non-interest income		23,810	23,994	23,765
Mortgage banking		2,568	3,221	3,897
(Loss) on sale of securities available for sale			(232)
Bank owned life insurance		1,129	1,159	871
Total non-interest income		45,346	44,499	42,920
Non-interest expenses
Compensation		46,104	42,581	40,814
Employee benefits		10,098	9,987	8,368
Net occupancy and equipment		7,653	7,393	7,422
Technology and communication		8,897	7,957	7,040
Marketing and business development		3,099	2,716	2,464
Postage, printing and supplies		1,558	1,475	1,521
Legal and professional		2,614	2,393	1,869
FDIC insurance		961	960	1,181
Amortization/impairment of investments in tax credit partnerships		1,237	7,124	4,458
Capital and deposit based taxes		3,325	3,440	2,800
Other		3,963	4,394	3,001
Total non-interest expenses		89,509	90,420	80,938
Income before income taxes		67,548	55,182	56,271
Income tax expense		12,031	17,139	15,244
Net income		$ 55,517	$ 38,043	$ 41,027
Net income per share, basic (in dollars per share)		$ 2.45	$ 1.69	$ 1.84
Net income per share, diluted (in dollars per share)		$ 2.42	$ 1.66	$ 1.80
Average common shares:
Basic (in shares)		22,619	22,532	22,356
Diluted (in shares)		22,944	22,983	22,792
Fiduciary and Trust [Member]
Non-interest income:
Non-interest income		$ 21,536	$ 20,505	$ 19,155
Deposit Account [Member]
Non-interest income:
Non-interest income		5,759	6,172	6,037
Credit and Debit Card [Member]
Non-interest income:
Non-interest income		6,769	5,979	5,655
Treasury Management [Member]
Non-interest income:
Non-interest income		4,571	4,297	3,867
Investment Advisory, Management and Administrative Service [Member]
Non-interest income:
Non-interest income		1,677	1,629	1,563
Product and Service, Other [Member]
Non-interest income:
Non-interest income	[1]	$ 1,337	$ 1,769	$ 1,875

[1] Includes safe box deposit fees of $177 thousand, $165 thousand, and $168 thousand included within the scope of ASC 606 in 2018, 2017, and 2016, respectively