Loans and Allowance for Credit Losses on Loans (Activity in Allowance for Loan Losses by Portfolio Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 25,171	$ 24,712	$ 24,171
Loans charged off	(1,838)	(2,713)	(2,248)
Recoveries	1,084	310	1,944
Provision (credit)	13,215	2,862	845
Ending balance	37,865	25,171	24,712
Ending Balance: Individually evaluated for impairment		463	824
Ending Balance: Collectively evaluated for impairment		24,708	23,888
Ending Balance: Individually evaluated for impairment		4,478	6,926
Ending Balance: Collectively evaluated for impairment		3,090,545	3,019,296
Total loan balances	3,219,822	3,095,023	3,026,222
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	5,842	6,071	5,086
Loans charged off	(121)	(462)	(173)
Recoveries	292	16	90
Provision (credit)	(1,410)	217	1,068
Ending balance	3,474	5,842	6,071
Ending Balance: Individually evaluated for impairment		364	586
Ending Balance: Collectively evaluated for impairment		5,478	5,485
Ending Balance: Individually evaluated for impairment		3,384	4,762
Ending Balance: Collectively evaluated for impairment		1,066,990	988,104
Total loan balances	1,054,798	1,070,374	992,866
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	12,414	11,654	11,863
Loans charged off		(300)	(512)
Recoveries		49	28
Provision (credit)		1,011	275
Ending balance		12,414	11,654
Ending Balance: Individually evaluated for impairment		30	23
Ending Balance: Collectively evaluated for impairment		12,384	11,631
Ending Balance: Individually evaluated for impairment		402	930
Ending Balance: Collectively evaluated for impairment		1,242,995	1,268,603
Total loan balances		1,243,397	1,269,533
Commercial
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	3,985	3,957	4,622
Loans charged off	(1,130)	(1,238)	(991)
Recoveries	572	225	1,771
Provision (credit)	1,728	1,041	(1,445)
Ending balance	6,703	3,985	3,957
Ending Balance: Individually evaluated for impairment			53
Ending Balance: Collectively evaluated for impairment		3,985	3,904
Ending Balance: Individually evaluated for impairment		319	786
Ending Balance: Collectively evaluated for impairment		442,382	414,650
Total loan balances	381,494	442,701	415,436
Home equity
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	2,423	2,796	2,367
Loans charged off	(317)	(412)	(476)
Recoveries	33	1	44
Provision (credit)	(315)	38	861
Ending balance	2,616	2,423	2,796
Ending Balance: Individually evaluated for impairment		69	162
Ending Balance: Collectively evaluated for impairment		2,354	2,634
Ending Balance: Individually evaluated for impairment		373	442
Ending Balance: Collectively evaluated for impairment		312,406	327,321
Total loan balances	258,573	312,779	327,763
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	507	234	233
Loans charged off	(167)	(301)	(96)
Recoveries	67	19	11
Provision (credit)	206	555	86
Ending balance	393	507	234
Ending Balance: Collectively evaluated for impairment		507	234
Ending Balance: Individually evaluated for impairment			6
Ending Balance: Collectively evaluated for impairment		25,772	20,618
Total loan balances	$ 20,392	$ 25,772	$ 20,624

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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Amount before allowance and after deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements.

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