Loans (Recorded Investment by Loan Class in Current and Nonaccrual Loans) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	$ 2,454	$ 7,994
Investment securities, nonaccrual	9,404	9,286
Current	3,605,336	3,540,628
Total Loans	3,617,194	3,557,908
Nonaccrual with no allowance	8,365	8,616
30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,819	6,209
60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	351	1,554
Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	284	231
Commercial Business [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	75	351
Investment securities, nonaccrual	1,742	1,975
Current	820,682	796,083
Total Loans	822,499	798,409
Nonaccrual with no allowance	1,238	1,502
Commercial Business [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	75	264
Commercial Business [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans		87
Commercial Mortgage [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	24	848
Investment securities, nonaccrual	3,402	2,906
Current	1,275,891	1,252,771
Total Loans	1,279,317	1,256,525
Nonaccrual with no allowance	2,867	2,709
Commercial Mortgage [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	24	822
Commercial Mortgage [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans		26
Residential Real Estate Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	188	1,044
Investment securities, nonaccrual	2,519	2,587
Current	585,295	582,906
Total Loans	588,002	586,537
Nonaccrual with no allowance	2,519	2,587
Residential Real Estate Loans [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	168	984
Residential Real Estate Loans [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	20	60
Residential Real Estate Lines [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	52	55
Investment securities, nonaccrual	256	323
Current	82,011	86,330
Total Loans	82,319	86,708
Nonaccrual with no allowance	256	323
Residential Real Estate Lines [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	27	40
Residential Real Estate Lines [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	25	15
Consumer Indirect [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,680	5,314
Investment securities, nonaccrual	1,482	1,495
Current	826,200	806,007
Total Loans	829,362	812,816
Nonaccrual with no allowance	1,482	1,495
Consumer Indirect [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	1,427	3,966
Consumer Indirect [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	253	1,348
Other Consumer [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	435	382
Investment securities, nonaccrual	3
Current	15,257	16,531
Total Loans	15,695	16,913
Nonaccrual with no allowance	3
Other Consumer [Member] | 30 to 59 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	98	133
Other Consumer [Member] | 60 to 89 Days Past Due [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	53	18
Other Consumer [Member] | Greater than 90 Days [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Past Due Loans	$ 284	$ 231