Loans (Summary of Loans) (Details) (USD $)	Jun. 30, 2013		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	$ 1,310,114,000		$ 1,252,419,000
Residential real estate	748,871,000		717,681,000
Consumer	325,995,000		323,903,000
Total loans	2,384,980,000	[1]	2,294,003,000	[1]
Percent of Total Loans	100.00%	[1]	100.00%	[1]
Net unamortized loan orgination costs	439,000		39,000
Net unamortized premiums on pruchased loans	97,000		83,000
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral, FHLBB	213,900,000		238,600,000
Commercial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral, FHLBB	48,100,000		51,800,000
Loans Pledged as Collateral, Federal Reserve Bank	24,900,000		29,500,000
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral, FHLBB	658,600,000		627,400,000
Home Equity Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans pledged as collateral, FHLBB	190,800,000		189,400,000
Commercial Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	1,310,114,000		1,252,419,000
Percent of Total Loans	55.00%		55.00%
Commercial Segment [Member] | Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	758,437,000	[2]	710,813,000	[2]
Percent of Total Loans	32.00%	[2]	31.00%	[2]
Commercial Segment [Member] | Commercial Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	39,449,000	[3]	27,842,000	[3]
Percent of Total Loans	2.00%	[3]	1.00%	[3]
Commercial Segment [Member] | Commercial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	512,228,000	[4]	513,764,000	[4]
Percent of Total Loans	21.00%	[4]	23.00%	[4]
Residential Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	748,871,000		717,681,000
Percent of Total Loans	31.00%		31.00%
Residential Segment [Member] | Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	728,158,000	[5]	692,798,000	[5]
Percent of Total Loans	30.00%	[5]	30.00%	[5]
Residential Segment [Member] | Homeowner Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	20,713,000		24,883,000
Percent of Total Loans	1.00%		1.00%
Consumer Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	325,995,000		323,903,000
Percent of Total Loans	14.00%		14.00%
Consumer Segment [Member] | Home Equity Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	228,367,000	[6]	226,861,000	[6]
Percent of Total Loans	10.00%	[6]	10.00%	[6]
Consumer Segment [Member] | Home Equity Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	41,312,000	[6]	39,329,000	[6]
Percent of Total Loans	2.00%	[6]	2.00%	[6]
Consumer Segment [Member] | Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	$ 56,316,000	[7]	$ 57,713,000	[7]
Percent of Total Loans	2.00%	[7]	2.00%	[7]

[1] Includes net unamortized loan origination costs of $439 thousand and $39 thousand, respectively, and net unamortized premiums on purchased loans of $97 thousand and $83 thousand, respectively, at June 30, 2013 and December 31, 2012.

[2] Amortizing mortgages and lines of credit, primarily secured by income producing property. As of June 30, 2013 and December 31, 2012, $213.9 million and $238.6 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit.

[3] Loans for construction of residential and commercial properties and for land development.

[4] Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate. As of June 30, 2013, $48.1 million and $24.9 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit and were collateralized for the discount window at the Federal Reserve Bank. Comparable amounts for December 31, 2012 were $51.8 million and $29.5 million, respectively.

[5] As of June 30, 2013 and December 31, 2012, $658.6 million and $627.4 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit.

[6] As of June 30, 2013 and December 31, 2012, $190.8 million and $189.4 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit.

[7] Fixed-rate consumer installment loans.