Commitments and Contingencies (Details) (USD $)		9 Months Ended
	Sep. 30, 2013 charge_count Plantiff	Sep. 30, 2013 Maximum	Sep. 30, 2013 Minimum	Sep. 30, 2013 Roseman v. Martin Sigillito Minimum	Sep. 30, 2013 Commitments to extend credit	Dec. 31, 2012 Commitments to extend credit	Sep. 30, 2013 Standby letters of credit	Dec. 31, 2012 Standby letters of credit	Sep. 30, 2013 Unadvanced Commitment on Impaired Loan	Dec. 31, 2012 Unadvanced Commitment on Impaired Loan	Sep. 30, 2013 Fixed Rate Loan Commitment Commitments to extend credit	Dec. 31, 2012 Fixed Rate Loan Commitment Commitments to extend credit
Schedule of Commitments [Line Items]
Remaing Term of Letters Of Credit		5 years	6 months
Loans and Leases Receivable, Impaired Loans, Commitment to Lend									$ 1,724,000	$ 775,000
Estimated losses attributable to unadvanced commitments on impaired loans									241,000	124,000
Off-balance sheet financial instruments, contractual amounts					769,704,000	722,325,000	43,452,000	42,561,000			38,600,000	50,700,000
Loss contingency, damages sought, value				$ 44,000,000
Number of counts found guilty	20
Number of lawsuits, bank as defendant	41