Borrowings (Additional Information) (Details) - USD ($)	1 Months Ended		12 Months Ended
	Feb. 28, 2021	Apr. 30, 2006	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2006	Dec. 31, 2015	Oct. 08, 2015	Dec. 31, 2008
Short-term Debt [Line Items]
Federal Home Loan Bank, Advances, General Debt Obligations, Disclosures, Collateral Pledged			$ 1,300,000,000	$ 1,400,000,000
Line of credit, maximum borrowing capacity			$ 10,000,000.0
Line of credit, expiration date			Dec. 17, 2021
Security Owned and Pledged as Collateral, Fair Value			$ 507,100,000	712,400,000
Securities Sold under Agreements to Repurchase			162,439,000	237,984,000
Amortization of Debt Issuance Costs			251,000	115,000
Interest on subordinated debentures			3,512,000	3,266,000	$ 3,415,000
Long-term Line of Credit			0
Federal Home Loan Bank Advances			$ 25,000,000	40,825,000
Debt Instrument, Term			10 years
Value Of Trust Preferred Securities Included In Tier One Capital			$ 43,000,000.0	43,000,000.0			$ 43,000,000.0
Subordinated Debt			59,331,000	59,080,000			15,000,000.0	$ 15,000,000.0
Subsequent Event [Member]
Short-term Debt [Line Items]
Payment for Debt Extinguishment or Debt Prepayment Cost	$ 514,000
Federal Home Loan Bank Advances [Member]
Short-term Debt [Line Items]
Line of credit, maximum borrowing capacity			9,900,000	9,900,000
Long-term Line of Credit			0
PNC [Member]
Short-term Debt [Line Items]
Line of credit, maximum borrowing capacity			50,000,000.0
Long-term Line of Credit			0
Federal Reserve Bank Advances [Member]
Short-term Debt [Line Items]
Line of credit, maximum borrowing capacity			54,200,000
Loans Pledged as Collateral			80,800,000
Security Owned and Pledged as Collateral, Fair Value			4,000
Long-term Line of Credit			$ 0
Junior Subordinated Debt
Short-term Debt [Line Items]
Percentage of trust preferred securities included in Tier I Capital ratio			9.60%
Value Of Trust Preferred Securities Included In Tier One Capital			$ 43,000,000.0
Subordinated Debentures [Member] | Subordinated Debt [Member]
Short-term Debt [Line Items]
Debt Issuance Costs, Net			0	251,000
Long-term borrowings			15,000,000	14,749,000
FHLBB Borrowing Maturing March 2025
Short-term Debt [Line Items]
Federal Home Loan Bank Advances			25,000,000.0
Tier II Capital [Member]
Short-term Debt [Line Items]
Subordinated Debt			$ 12,000,000.0	$ 15,000,000.0			$ 15,000,000.0
Subsidiary One [Member] | Junior Subordinated Debt
Short-term Debt [Line Items]
Debt Instrument, Interest Rate Terms		The contract interest rate of the trust preferred securities is three-month LIBOR plus 140 basis points.
Debt Instrument, Interest Rate, Stated Percentage			1.64%	3.36%
Value of outstanding common shares of subsidiary owned by company		$ 1,100,000
Proceeds from issuance of trust preferred securities		$ 36,100,000
Debt interest rate, additional rate over three month LIBOR		14000.00%
Long-term borrowings			$ 36,083,000	$ 36,083,000
Subsidiary Two [Member] | Junior Subordinated Debt
Short-term Debt [Line Items]
Debt Instrument, Interest Rate Terms						The contract interest rate of the trust preferred securities is the average three-month LIBOR plus 1.42%.
Debt Instrument, Interest Rate, Stated Percentage			1.66%	3.41%
Value of outstanding common shares of subsidiary owned by company						$ 248,000
Trust preferred securities assumed in acquisition									$ 8,000,000.0
Aggregate amount of junior subordinated debt issued to subsidiary by acquired company, prior to acquisition						$ 8,200,000
Debt Instrument, Term						30 years
Debt interest rate, additional rate over three month LIBOR						142.00%
Long-term borrowings			$ 8,248,000	$ 8,248,000