Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified		9 Months Ended			9 Months Ended
	Sep. 30, 2012 charge_count	Sep. 30, 2012 Maximum	Sep. 30, 2012 Minimum	Sep. 30, 2012 Distinctive Notes lawsuit	Sep. 30, 2012 Roseman v. Martin Sigillito Minimum	Sep. 30, 2012 BJD, LLC and Barbara Dunning v. Enterprise Financial	Sep. 30, 2012 Commitments to extend credit	Dec. 31, 2011 Commitments to extend credit	Sep. 30, 2012 Standby letters of credit	Dec. 31, 2011 Standby letters of credit	Sep. 30, 2012 Unadvanced Commitment on Impaired Loan	Sep. 30, 2012 Fixed Rate Loan Commitment Commitments to extend credit	Dec. 31, 2011 Fixed Rate Loan Commitment Commitments to extend credit	Sep. 30, 2012 Credit Lines With Usage Restrictions [Member] Commitments to extend credit
Schedule of Commitments [Line Items]
Loans and Leases Receivable, Impaired Loans, Commitment to Lend											$ 543
Estimated losses attributable to unadvanced commitments on impaired loans											98
Off-balance sheet financial instruments, contractual amounts							724,517	547,657	43,383	43,973		66,300	75,700	106,000
Remaining term of letters of credit		5 years	6 months
Number of lawsuits, bank as defendant				2
Loss contingency, damages sought, value					$ 44,000	$ 800
Interest rate on damages sought						9.00%
Number of counts found guilty	20