Consolidated Statements of Cash Flows	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Operating activities:
Net income	$ 34,767,000	$ 53,695,000	$ 46,255,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and accretion, net	25,639,000	17,861,000	18,204,000
Provision for credit losses	26,254,000	2,504,000	5,448,000
Bank owned life insurance income	(1,977,000)	(2,430,000)	(1,955,000)
Net loss (gain) on investment securities	368,000	(164,000)	146,000
Loans originated for sale	(260,974,000)	(156,058,000)	(123,134,000)
Proceeds from sales of loans	268,363,000	157,752,000	124,796,000
Net gains on sales of loans	(6,446,000)	(3,667,000)	(2,846,000)
Deferred income tax (benefit) expense	(8,101,000)	109,000	(309,000)
Increase in accrued expenses	799,000	366,000	147,000
(Increase) decrease in interest receivable	(865,000)	613,000	(854,000)
Increase (decrease) in other assets	1,006,000	(1,227,000)	(533,000)
Non cash lease expense	47,000	55,000
Other, net	7,263,000	(1,421,000)	10,085,000
Net cash provided by operating activities	85,483,000	67,157,000	75,243,000
Available-for-sale investment securities:
Purchases	(261,395,000)	(271,924,000)	(137,818,000)
Proceeds from sales	82,610,000	72,706,000	14,489,000
Proceeds from principal payments, calls and prepayments	356,854,000	199,870,000	122,986,000
Held-to-maturity investment securities:
Purchases	(40,112,000)	0	0
Proceeds from principal payments	5,123,000	4,945,000	4,281,000
Other investment securities:
Purchases	(6,261,000)	(3,114,000)	(2,689,000)
Proceeds from sales	12,180,000	7,340,000	7,622,000
Proceeds from insurance claim	0	26,000
Net increase in loans held for investment	444,128,000	10,661,000	134,071,000
Net expenditures for premises and equipment	(4,299,000)	(2,809,000)	(4,531,000)
Proceeds from sales of other real estate owned	269,000	239,000	278,000
Proceeds from bank owned life insurance	108,000	1,642,000
Business acquisitions, net of cash received	(94,856,000)	7,814,000	4,695,000
Investment in limited partnership and tax credit funds	(12,000)	(5,021,000)	(5,398,000)
Net cash (used in) provided by investing activities	(393,919,000)	1,053,000	(130,156,000)
Financing activities:
Net increase in non-interest-bearing deposits	326,115,000	4,832,000	22,380,000
Net increase in interest-bearing deposits	292,822,000	72,841,000	3,449,000
Net (decrease) increase in short-term borrowings	(263,716,000)	(76,809,000)	61,883,000
Proceeds from long-term borrowings	50,000,000	0	0
Payments on long-term borrowings	(2,715,000)	(3,501,000)	(4,591,000)
Cash dividends paid	(27,052,000)	(25,942,000)	(20,915,000)
Repurchase of treasury stock under share repurchase program	(29,281,000)	(805,000)	0
Purchase of treasury stock in connection with employee incentive program and compensation plan for Boards of Directors to be held as treasury stock	1,128,000	845,000	1,380,000
Proceeds from issuance of common shares	594,000	6,000	25,000
Contingent consideration payments made after a business acquisition	(296,000)	(406,000)	(520,000)
Net cash provided by (used in) financing activities	345,343,000	(30,629,000)	60,331,000
Net increase in cash, cash equivalents and restricted cash	36,907,000	37,581,000	5,418,000
Cash, cash equivalents and restricted cash at beginning of period	115,193,000	77,612,000	72,194,000
Cash, cash equivalents, and restricted cash at end of period	152,100,000	115,193,000	77,612,000
Supplemental cash flow information:
Interest paid	18,939,000	28,887,000	19,920,000
Income taxes paid	12,500,000	11,450,000	6,135,000
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Transfers from loans to other real estate owned	296,000	153,000	90,000
Lease right-of-use assets obtained in exchange for lessee operating lease liabilities	62,000	3,701,000
Other Real Estate Owned	134,000	227,000
Servicing rights (b)(c)	2,486,000	2,742,000	2,655,000
Level 1 | Nonrecurring Basis
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Impaired Financing Receivable, Fair Value Disclosure	0	0
Other Real Estate Owned	0	0
Servicing rights (b)(c)	0	0
Level 2 | Nonrecurring Basis
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Impaired Financing Receivable, Fair Value Disclosure	0	0
Other Real Estate Owned	0	0
Servicing rights (b)(c)	0	0
Level 3 | Nonrecurring Basis
Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]
Impaired Financing Receivable, Fair Value Disclosure	0	29,100,000
Other Real Estate Owned	134,000	227,000
Servicing rights (b)(c)	2,591,000	3,881,000
Accounting Standards Update 2016-01 [Member]
Adjustments to reconcile net income to net cash provided by operating activities:
Fair value adjustment on equity investment securities	$ (660,000)	$ (831,000)	$ (207,000)