Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Loans and leases, including fees		$ 134,342	$ 118,467	$ 99,924
Federal funds sold and interest bearing due from banks		2,933	1,307	1,330
Mortgage loans held for sale		182	166	191
Securities available for sale
Taxable		9,839	9,001	8,365
Tax-exempt		469	832	1,089
Total interest income		147,765	129,773	110,899
Interest expense:
Deposits		20,560	13,441	5,975
Securities sold under agreements to repurchase and other short-term borrowings		318	992	316
Federal Home Loan Bank advances		1,640	924	955
Subordinated debentures		26	0	0
Total interest expense		22,544	15,357	7,246
Net interest income		125,221	114,416	103,653
Provision for loan and lease losses		1,000	2,705	2,550
Net interest income after provision		124,221	111,711	101,103
Non-interest income:
Non-interest income		22,643	21,536	20,505
Mortgage banking income	[1]	3,090	2,568	3,221
Loss on sale of securities available for sale		0	0	(232)
Bank owned life insurance	[1]	1,031	1,129	1,159
Total non-interest income		49,790	45,346	44,499
Non-interest expenses:
Compensation		50,319	46,104	42,581
Employee benefits		11,038	10,098	9,987
Net occupancy and equipment		8,417	7,653	7,393
Technology and communication		9,591	8,897	7,957
Marketing and business development		3,627	3,099	2,716
Postage, printing and supplies		1,652	1,558	1,475
Legal and professional		3,014	2,614	2,393
FDIC insurance		245	961	960
Amortization of investments in tax credit partnerships		1,078	1,237	7,124
Capital and deposit based taxes		3,870	3,325	3,440
Other		5,500	3,963	4,394
Total non-interest expenses		98,351	89,509	90,420
Income before income tax expense		75,660	67,548	55,182
Income tax expense		9,593	12,031	17,139
Net income		$ 66,067	$ 55,517	$ 38,043
Net income per share, basic (in dollars per share)		$ 2.92	$ 2.45	$ 1.69
Net income per share, diluted (in dollars per share)		$ 2.89	$ 2.42	$ 1.66
Weighted average outstanding shares:
Basic (in shares)		22,598	22,619	22,532
Diluted (in shares)		22,865	22,944	22,983
Fiduciary and Trust [Member]
Non-interest income:
Non-interest income		$ 22,643	$ 21,536	$ 20,505
Deposit Account [Member]
Non-interest income:
Non-interest income		5,513	5,759	6,172
Credit and Debit Card [Member]
Non-interest income:
Non-interest income		8,123	6,769	5,979
Treasury Management [Member]
Non-interest income:
Non-interest income		4,992	4,571	4,297
Investment Advisory, Management and Administrative Service [Member]
Non-interest income:
Non-interest income		1,498	1,677	1,629
Product and Service, Other [Member]
Non-interest income:
Non-interest income		$ 2,900	$ 1,337	$ 1,769

[1] Outside of the scope of ASC 606