Consolidated Statements of Income - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Interest and fees on loans	$ 143,340,000	$ 125,263,000	$ 103,043,000
Interest and dividends on taxable investment securities	23,205,000	23,132,000	20,415,000
Interest on tax-exempt investment securities	2,631,000	2,467,000	2,923,000
Other interest income	919,000	402,000	144,000
Total interest income	170,095,000	151,264,000	126,525,000
Interest expense:
Interest on deposits	22,210,000	13,705,000	7,154,000
Interest on short-term borrowings	4,712,000	5,238,000	1,534,000
Interest on long-term borrowings	2,335,000	2,709,000	4,460,000
Total interest expense	29,257,000	21,652,000	13,148,000
Net interest income	140,838,000	129,612,000	113,377,000
Provision for loan losses	2,504,000	5,448,000	3,772,000
Net interest income after provision for loan losses	138,334,000	124,164,000	109,605,000
Non-interest income:
Insurance income	14,802,000	14,812,000	14,204,000
Mortgage banking income	4,328,000	3,333,000	1,872,000
Bank owned life insurance income	2,430,000	1,955,000	1,950,000
Net gain (loss) on investment securities	164,000	(146,000)	2,983,000
Net loss on asset disposals and other transactions	(782,000)	(334,000)	(63,000)
Other non-interest income (a)	2,565,000	2,655,000	1,865,000
Total non-interest income	64,274,000	56,754,000	55,573,000
Non-interest expense:
Salaries and employee benefit costs	77,860,000	69,308,000	60,276,000
Net occupancy and equipment expense	12,431,000	11,272,000	10,633,000
Electronic banking expense	7,186,000	6,057,000	5,874,000
Professional fees	7,095,000	7,862,000	6,575,000
Data processing and software expense	6,332,000	5,419,000	4,441,000
Amortization of other intangible assets	3,359,000	3,338,000	3,516,000
Franchise tax expense	3,071,000	2,771,000	2,246,000
Marketing expense	2,291,000	1,962,000	1,714,000
Foreclosed real estate and other loan expenses	1,956,000	1,431,000	873,000
Communication expense	1,181,000	1,265,000	1,475,000
FDIC insurance expense	602,000	1,546,000	1,816,000
Other non-interest expense	13,886,000	13,746,000	8,536,000
Total non-interest expense	137,250,000	125,977,000	107,975,000
Income before income taxes	65,358,000	54,941,000	57,203,000
Income tax expense	11,663,000	8,686,000	18,732,000
Net income	$ 53,695,000	$ 46,255,000	$ 38,471,000
Earnings per common share – basic	$ 2.65	$ 2.42	$ 2.12
Earnings per common share – diluted	$ 2.63	$ 2.41	$ 2.10
Weighted-average number of common shares outstanding – basic	20,120,119	18,991,768	18,050,189
Weighted-average number of common shares outstanding – diluted	20,273,725	19,122,260	18,208,684
Fiduciary and Trust [Member]
Non-interest income:
Revenue from contract with customer, including assessed tax	$ 13,159,000	$ 12,543,000	$ 11,558,000
Credit and Debit Card [Member]
Non-interest income:
Revenue from contract with customer, including assessed tax	13,680,000	11,477,000	10,358,000
Deposit Account [Member]
Non-interest income:
Revenue from contract with customer, including assessed tax	11,700,000	9,778,000	9,614,000
Interest Rate Swap | transaction fee [Member]
Non-interest income:
Revenue from contract with customer, including assessed tax	2,228,000	681,000	1,232,000
Adjustments for New Accounting Pronouncement [Member]
Non-interest expense:
Income tax expense	700,000	700,000	$ 900,000
Fair value adjustment on equity investment securities	$ (831,000)	$ (207,000)