Borrowings (Narrative) (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Borrowings [Abstract]
Federal Home Loan Bank advances modification first amount	$ 31,100,000
Sale of mortgage-backed securities in balance sheet management transaction	6,000,000
Federal Home Loan Bank advances prepayment first amount	5,000,000
Sale of mortgage-backed securities net realized gains recorded for balance sheet management transaction	217,000
Federal Home Loan Bank advances prepayment first penalty	203,000
Federal Home Loan Bank advances prepayment second amount	10,000,000
Federal Home Loan Bank advances prepayment second penalty	758,000
Federal Home Loan Bank advances modification second amount	36,700,000
Federal Home Loan Bank advances prepayment third amount	32,400,000
Federal Home Loan Bank advances prepayment third penalty	1,200,000
Federal Home Loan Bank ddvances modification third amount	13,000,000
Federal Home Loan Bank advances	417,700,000	540,500,000
Unused line of credit with Federal Home Loan Bank	8,000,000
Securities available for sale and held to maturity included in collateral to Federal Home Loan Bank	284,100,000	320,800,000
Loans pledged as collateral, FHLBB	1,100,000,000	911,500,000
Securities sold under repurchase agreements		$ 19,500,000