Allowance for Credit Losses on Loans (Allowance for Loan Losses Rollforward Analysis) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		$ 41,441	$ 27,398	$ 27,014	$ 27,072
Adoption of Topic 326	[1]					$ 6,501
Charge-offs		(111)	(966)	(1,072)	(1,888)
Recoveries		15	165	45	238
Provision		1,300	400	10,157	1,575
Allowance, Ending Balance		42,645	26,997	42,645	26,997
Commercial Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		20,283	16,882	14,741	15,381
Adoption of Topic 326	[1]					3,405
Charge-offs		0	(947)	(172)	(947)
Recoveries		0	0	0	0
Provision		1,474	866	3,783	2,367
Allowance, Ending Balance		21,757	16,801	21,757	16,801
Commercial & Industrial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		11,278	4,453	3,921	5,847
Adoption of Topic 326	[1]					3,029
Charge-offs		(2)	(1)	(585)	(19)
Recoveries		2	123	11	151
Provision		(93)	(1,128)	4,809	(2,532)
Allowance, Ending Balance		11,185	3,447	11,185	3,447
Total Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		31,561	21,335	18,662	21,228
Adoption of Topic 326	[1]					6,434
Charge-offs		(2)	(948)	(757)	(966)
Recoveries		2	123	11	151
Provision		1,381	(262)	8,592	(165)
Allowance, Ending Balance		32,942	20,248	32,942	20,248
Residential Real Estate
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		8,053	4,857	6,615	3,987
Adoption of Topic 326	[1]					221
Charge-offs		(99)	0	(99)	(486)
Recoveries		0	0	0	0
Provision		(35)	554	1,182	1,910
Allowance, Ending Balance		7,919	5,411	7,919	5,411
Home Equity
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		1,394	913	1,390	1,603
Adoption of Topic 326	[1]					(106)
Charge-offs		0	0	(174)	(372)
Recoveries		4	36	11	71
Provision		(51)	64	226	(289)
Allowance, Ending Balance		1,347	1,013	1,347	1,013
Other
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		433	293	347	254
Adoption of Topic 326	[1]					(48)
Charge-offs		(10)	(18)	(42)	(64)
Recoveries		9	6	23	16
Provision		5	44	157	119
Allowance, Ending Balance		437	325	437	325
Total Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Allowance, Beginning Balance		1,827	1,206	1,737	1,857
Adoption of Topic 326	[1]					$ (154)
Charge-offs		(10)	(18)	(216)	(436)
Recoveries		13	42	34	87
Provision		(46)	108	383	(170)
Allowance, Ending Balance		$ 1,784	$ 1,338	$ 1,784	$ 1,338

[1] Adoption of the CECL accounting standard effective January 1, 2020.