Loans and Allowance for Loan Losses (Activity in Allowance for Loan Losses by Portfolio Segment) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	$ 21,590,000	$ 23,044,000	$ 23,011,000
Loans charged off	(3,444,000)	(4,274,000)	(4,502,000)
Recoveries	746,000	768,000	744,000
Provision (credit)	2,224,000	2,052,000	3,791,000
Ending balance	21,116,000	21,590,000	23,044,000
Ending Balance: Individually evaluated for impairment	2,239,000	2,981,000	3,106,000
Ending Balance: Collectively evaluated for impairment	18,877,000	18,609,000	19,938,000
Ending Balance: Individually evaluated for impairment	21,179,000	27,947,000	27,157,000
Ending Balance: Collectively evaluated for impairment	1,751,431,000	1,552,455,000	1,536,709,000
Total ending loans balance	1,772,610,000	1,580,402,000	1,563,866,000
Residential real estate loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	5,603,000	6,996,000	6,398,000
Loans charged off	(785,000)	(1,059,000)	(1,197,000)
Recoveries	165,000	35,000	73,000
Provision (credit)	(84,000)	(369,000)	1,722,000
Ending balance	4,899,000	5,603,000	6,996,000
Ending Balance: Individually evaluated for impairment	1,220,000	1,750,000	2,255,000
Ending Balance: Collectively evaluated for impairment	3,679,000	3,853,000	4,741,000
Ending Balance: Individually evaluated for impairment	9,656,000	14,435,000	13,805,000
Ending Balance: Collectively evaluated for impairment	575,812,000	555,384,000	558,368,000
Total ending loans balance	585,468,000	569,819,000	572,173,000
Commercial real estate loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	4,374,000	4,549,000	5,702,000
Loans charged off	(361,000)	(952,000)	(593,000)
Recoveries	135,000	121,000	222,000
Provision (credit)	334,000	656,000	782,000
Ending balance	4,482,000	4,374,000	4,549,000
Ending Balance: Individually evaluated for impairment	251,000	526,000	265,000
Ending Balance: Collectively evaluated for impairment	4,231,000	3,848,000	4,284,000
Ending Balance: Individually evaluated for impairment	7,658,000	8,864,000	7,968,000
Ending Balance: Collectively evaluated for impairment	633,003,000	532,235,000	498,263,000
Total ending loans balance	640,661,000	541,099,000	506,231,000
Commercial loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	6,220,000	5,933,000	4,846,000
Loans charged off	(1,544,000)	(1,426,000)	(1,393,000)
Recoveries	395,000	495,000	406,000
Provision (credit)	1,752,000	1,218,000	2,074,000
Ending balance	6,823,000	6,220,000	5,933,000
Ending Balance: Individually evaluated for impairment	168,000	132,000	286,000
Ending Balance: Collectively evaluated for impairment	6,655,000	6,088,000	5,647,000
Ending Balance: Individually evaluated for impairment	1,853,000	2,635,000	3,610,000
Ending Balance: Collectively evaluated for impairment	255,662,000	176,568,000	186,844,000
Total ending loans balance	257,515,000	179,203,000	190,454,000
Home equity loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	2,403,000	2,520,000	2,704,000
Loans charged off	(611,000)	(647,000)	(1,234,000)
Recoveries	19,000	56,000	23,000
Provision (credit)	436,000	474,000	1,027,000
Ending balance	2,247,000	2,403,000	2,520,000
Ending Balance: Individually evaluated for impairment	496,000	433,000	261,000
Ending Balance: Collectively evaluated for impairment	1,751,000	1,970,000	2,259,000
Ending Balance: Individually evaluated for impairment	1,741,000	1,571,000	1,515,000
Ending Balance: Collectively evaluated for impairment	269,968,000	271,059,000	276,860,000
Total ending loans balance	271,709,000	272,630,000	278,375,000
Consumer loans
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	319,000	184,000	420,000
Loans charged off	(143,000)	(190,000)	(85,000)
Recoveries	32,000	61,000	20,000
Provision (credit)	73,000	264,000	171,000
Ending balance	281,000	319,000	184,000
Ending Balance: Individually evaluated for impairment	104,000	140,000	39,000
Ending Balance: Collectively evaluated for impairment	177,000	179,000	145,000
Ending Balance: Individually evaluated for impairment	271,000	442,000	259,000
Ending Balance: Collectively evaluated for impairment	16,986,000	17,209,000	16,374,000
Total ending loans balance	17,257,000	17,651,000	16,633,000
Unallocated
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Beginning balance	2,671,000	2,862,000	2,941,000
Provision (credit)	(287,000)	(191,000)	79,000
Ending balance	2,384,000	2,671,000	2,862,000
Ending Balance: Collectively evaluated for impairment	$ 2,384,000	$ 2,671,000	$ 2,862,000