Loans and Allowance for Credit Losses on Loans (Loan Aging Analysis by Portfolio Segment (Including Loans Past Due Over Ninety Days and Non Accrual Loans) and Summary of Non Accrual Loans) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 8,787	$ 12,089
Current	3,211,035	3,082,934
Total loan balances	3,219,822	3,095,023	$ 3,026,222
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,044	5,522
Current	1,049,754	1,064,852
Total loan balances	1,054,798	1,070,374	992,866
Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		2,531
Current		1,240,866
Total loan balances		1,243,397	1,269,533
Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,287	1,496
Current	380,207	441,205
Total loan balances	381,494	442,701	415,436
Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,924	2,378
Current	256,649	310,401
Total loan balances	258,573	312,779	327,763
Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	163	162
Current	20,229	25,610
Total loan balances	20,392	25,772	$ 20,624
Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	223
Current	1,097,752
Total loan balances	1,097,975
Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	146
Current	271,349
Total loan balances	271,495
SBA PPP Portfolio Segment
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current	135,095
Total loan balances	135,095
30 – 59 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,362	3,901
30 – 59 Days Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,406	2,297
30 – 59 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		267
30 – 59 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	430	548
30 – 59 Days Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	335	681
30 – 59 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	92	108
30 – 59 Days Past Due | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	99
60 – 89 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,393	2,859
60 – 89 Days Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,103	627
60 – 89 Days Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		1,720
60 – 89 Days Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		243
60 – 89 Days Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	173	238
60 – 89 Days Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	67	31
60 – 89 Days Past Due | Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	50
90 Days or Greater Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	5,032	5,329
90 Days or Greater Past Due | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	2,535	2,598
90 Days or Greater Past Due | Commercial real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due		544
90 Days or Greater Past Due | Commercial
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	857	705
90 Days or Greater Past Due | Home equity
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	1,416	1,459
90 Days or Greater Past Due | Consumer
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	4	$ 23
90 Days or Greater Past Due | Commercial Real Estate - Non-Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	173
90 Days or Greater Past Due | Commercial Real Estate - Owner Occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total Past Due	$ 47