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Loans (Recorded Investment by Loan Class in Current and Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	$ 7,994	$ 7,081
Investment securities, nonaccrual	9,286	8,634
Current	3,540,628	3,163,750
Total Loans	3,557,908	3,179,465	$ 3,044,320
Nonaccrual with no allowance	8,616
Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	351	361
Investment securities, nonaccrual	1,975	1,177
Current	796,083	569,684
Total Loans	798,409	571,222	557,040
Nonaccrual with no allowance	1,502
Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	848	531
Investment securities, nonaccrual	2,906	3,146
Current	1,252,771	1,104,638
Total Loans	1,256,525	1,108,315	960,265
Nonaccrual with no allowance	2,709
Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,044	1,043
Investment securities, nonaccrual	2,587	2,484
Current	582,906	557,190
Total Loans	586,537	560,717	514,981
Nonaccrual with no allowance	2,587
Residential Real Estate Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	55	268
Investment securities, nonaccrual	323	102
Current	86,330	100,678
Total Loans	86,708	101,048	106,712
Nonaccrual with no allowance	323
Consumer Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	5,314	4,748
Investment securities, nonaccrual	1,495	1,725
Current	806,007	815,706
Total Loans	812,816	822,179	888,732
Nonaccrual with no allowance	1,495
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	382	130
Current	16,531	15,854
Total Loans	16,913	15,984	$ 16,590
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	6,209	5,897
30 to 59 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	264	361
30 to 59 Days Past Due [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	822	531
30 to 59 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	984	929
30 to 59 Days Past Due [Member] | Residential Real Estate Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	40	231
30 to 59 Days Past Due [Member] | Consumer Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	3,966	3,729
30 to 59 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	133	116
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,554	1,178
60 to 89 Days Past Due [Member] | Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	87
60 to 89 Days Past Due [Member] | Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	26
60 to 89 Days Past Due [Member] | Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	60	114
60 to 89 Days Past Due [Member] | Residential Real Estate Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	15	37
60 to 89 Days Past Due [Member] | Consumer Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,348	1,019
60 to 89 Days Past Due [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	18	8
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	231	6
Greater than 90 Days [Member] | Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	$ 231	$ 6

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