Borrowings (Narrative) (Details) (USD $)	6 Months Ended
Jun. 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	523,989,000	540,450,000
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	305,900,000	320,800,000
Loans pledged as collateral, FHLBB	907,200,000	911,500,000
Securities sold under repurchase agreements		$ 19,500,000

Aggregate carrying value of assets sold under agreements to repurchase when the carrying amount (or market value, if higher than the carrying amount) of securities or other assets sold under repurchase agreements exceeds 10 percent of total assets, as of the most recent balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 4

-Section 08

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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-Subparagraph (SX 210.4-08.(m)(1)(i)(A)(i))

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The aggregate carrying amount of all Federal Home Loan Bank loans (advances).

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States the total dollar amount of advances or credit lines available as of the Balance Sheet date from the Federal Home Loan Bank system.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-Name Statement of Position (SOP)

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-Publisher FASB

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States the amount of the collateral pledged in support of Federal Home Loan Bank advances outstanding as of the Balance Sheet date.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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-Publisher FASB

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Carrying amount as of the balance sheet date of loans that have been pledged as collateral for borrowings. If the secured party has the right by contract or custom to sell or re-pledge the collateral, then the debtor reclassifies that asset and report that asset in its statement of financial position separately from other assets not so encumbered.

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The first amount of Federal Home Loan Bank advances modified.

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The second amount of Federal Home Loan Bank advances modified.

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The first amount of Federal Home Loan Bank advances prepaid.

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The first amount of Federal Home Loan Bank advances prepayment penalty.

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The second amount of Federal Home Loan Bank advances prepaid.

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The second amount of Federal Home Loan Bank advances prepayment penalty.

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The amount of mortgage-backed securities sold in connection with a balance sheet management transaction.

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The amount net realized gains on mortgage-backed securities sold in connection with a balance sheet management transaction.

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