Borrowings (Narrative) (Details) $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($)
Federal Reserve Bank Of Boston's [Member]
Federal Home Loan Bank, Advances [Line Items]
Overnight borrowings	$ 60.0
Interest rate on overnight borrowings	0.25%
Federal Home Loan Bank Of Boston [Member]
Federal Home Loan Bank, Advances [Line Items]
Aggregate borrowings from FHLB	$ 13.5
Federal Home Loan Bank Of Boston [Member] \| Minimum [Member]
Federal Home Loan Bank, Advances [Line Items]
Interest rates on FHLB advances ranged from	1.21%
Term of FHLB borrowings	1 year
Federal Home Loan Bank Of Boston [Member] \| Maximum [Member]
Federal Home Loan Bank, Advances [Line Items]
Interest rates on FHLB advances ranged from	3.01%
Federal Home Loan Bank Of Boston [Member] \| Weighted Average [Member]
Federal Home Loan Bank, Advances [Line Items]
Interest rates on FHLB advances ranged from	2.12%

Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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-Name Accounting Standards Codification
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-SubTopic 470
-Section 45
-Paragraph 1
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Contractual interest rate for funds borrowed, under the debt agreement.

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Discloses the single interest rate [if] applicable to the advances from the Federal Home Loan Bank, by branch, as of the Balance Sheet date.

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Amount of borrowings classified as other, maturing within one year or the normal operating cycle, if longer.

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