Loans (Summary of Loans) (Details) (USD $)	Dec. 31, 2013		Dec. 31, 2012
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	$ 1,363,335,000		$ 1,252,419,000
Residential real estate	772,674,000		717,681,000
Consumer	326,875,000		323,903,000
Total loans	2,462,884,000	[1]	2,294,003,000	[1]
Percent of total loans	100.00%	[1]	100.00%	[1]
Net unamortized loan origination costs	879,000		39,000
Net unamortized premiums on purchased loans	99,000		83,000
Commercial Mortgages [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	796,249,000	[2]	710,813,000	[2]
Total loans	796,249,000		710,813,000
Percent of total loans	32.00%	[2]	31.00%	[2]
Loans pledged as collateral, FHLBB and letters of credit	190,700,000		238,600,000
Commercial Construction and Development [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	36,289,000	[3]	27,842,000	[3]
Total loans	36,289,000		27,842,000
Percent of total loans	1.00%	[3]	1.00%	[3]
Commercial Other [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	530,797,000	[4]	513,764,000	[4]
Total loans	530,797,000		513,764,000
Percent of total loans	22.00%	[4]	23.00%	[4]
Loans pledged as collateral, FHLBB and letters of credit	44,100,000		51,800,000
Loans pledged as collateral, Federal Reserve Bank	21,200,000		29,500,000
Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial	1,363,335,000		1,252,419,000
Percent of total loans	55.00%		55.00%
Residential Mortgage [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	749,163,000	[5]	692,798,000	[5]
Total loans	749,163,000		692,798,000
Percent of total loans	30.00%	[5]	30.00%	[5]
Loans pledged as collateral, FHLBB and letters of credit	684,600,000		627,400,000
Homeowner Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	23,511,000		24,883,000
Total loans	23,511,000		24,883,000
Percent of total loans	1.00%		1.00%
Residential Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Residential real estate	772,674,000		717,681,000
Percent of total loans	31.00%		31.00%
Home Equity Lines [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	231,362,000	[6]	226,861,000	[6]
Total loans	231,362,000		226,861,000
Percent of total loans	9.00%	[6]	10.00%	[6]
Loans pledged as collateral, FHLBB and letters of credit	195,300,000		189,400,000
Home Equity Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	40,212,000	[6]	39,329,000	[6]
Total loans	40,212,000		39,329,000
Percent of total loans	2.00%	[6]	2.00%	[6]
Other Consumer [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	55,301,000	[7]	57,713,000	[7]
Total loans	55,301,000		57,713,000
Percent of total loans	3.00%	[7]	2.00%	[7]
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Consumer	$ 326,875,000		$ 323,903,000
Percent of total loans	14.00%		14.00%

[1] Includes net unamortized loan origination costs of $879 thousand and $39 thousand, respectively, and net unamortized premiums on purchased loans of $99 thousand and $83 thousand, respectively, at December 31, 2013 and 2012.

[2] Amortizing mortgages and lines of credit, primarily secured by income producing property. As of December 31, 2013 and 2012, $190.7 million and $238.6 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit.

[3] Loans for construction commercial properties, loans to developers for construction of residential properties and loans for land development.

[4] Loans to businesses and individuals, a substantial portion of which are fully or partially collateralized by real estate. As of December 31, 2013, $44.1 million and $21.2 million, respectively, were pledged as collateral for FHLBB borrowings and letters of credit and were collateralized for the discount window at the FRB. Comparable amounts for December 31, 2012 were $51.8 million and $29.5 million, respectively.

[5] As of December 31, 2013 and 2012, $684.6 million and $627.4 million, respectively were pledged as collateral for FHLBB borrowings and letters of credit.

[6] As of December 31, 2013 and 2012, $195.3 million and $189.4 million, respectively were pledged as collateral for FHLBB borrowings and letters of credit.

[7] Fixed rate consumer installment loans.