Allowance for Credit Losses and Credit Quality Information - Additional Information (Details)	12 Months Ended
	Dec. 31, 2020 USD ($) SecurityLoan loan	Dec. 31, 2019 USD ($) SecurityLoan loan	Dec. 31, 2018 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Interest income on impaired loans	$ 800,000	$ 800,000
Loan workout and other credit costs	6,899,000	3,616,000	$ 1,470,000
Troubled debt restructuring related reserves	100,000	600,000
Decrease in allowance for loan losses	500,000	200,000
Troubled debt restructurings charged off	$ 0	$ 0
TRD defaulted | loan	0	4
Subsequent default, loan amount		$ 300,000
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans in the process of foreclosure | SecurityLoan	27	33
Total loans outstanding, residential loans	$ 1,900,000	$ 3,200,000
Gross loans	$ 774,455,000	$ 1,016,500,000
Total Commercial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans in the process of foreclosure | SecurityLoan	23	29
Total loans outstanding, residential loans	$ 12,800,000	$ 9,500,000
Total Commercial | Paycheck Protection Program, CARES Act
Accounts, Notes, Loans and Financing Receivable [Line Items]
Gross loans	751,200,000
Residential and Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan workout and other credit costs	$ 3,200,000	$ 2,700,000	$ 1,500,000