Borrowings (Summary of Short term and Long term Borrowings and Subordinated Debentures) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase	$ 162,439	$ 237,984
Total short-term borrowings	$ 162,439	$ 268,809
FHLBB borrowings
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	0.98%	1.87%
Long-term Debt and Capital Lease Obligations, Repayments of Principal in Next Twelve Months	$ 0
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2021	0
2022	0
2023	0
2025	25,000
Customer repurchase agreements
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2021	162,439
FHLBB and correspondent bank overnight borrowings
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2021	$ 0
Long-term Debt
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	0.98%	1.87%
Long-term Debt and Capital Lease Obligations, Repayments of Principal in Next Twelve Months	$ 0
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2022	0
2023	0
2024	0
2025	25,000
Thereafter	0
Total long-term borrowings	$ 25,000	$ 10,000
Subordinated Debt and Junior Subordinated Debt
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	2.62%	3.90%
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2025	$ 15,000
Thereafter	44,331
Total long-term borrowings	$ 59,331	$ 59,080
Subordinated Debt \| Subordinated debentures
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	5.50%	5.50%
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2025	$ 15,000
Thereafter	0
Total long-term borrowings	15,000	$ 14,749
Debt Issuance Costs, Net	0	251
Short-term Debt
Debt Instrument [Line Items]
Total short-term borrowings	$ 162,439	$ 268,809
Weighted Average Rate (as a percent)	0.34%	1.28%
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
2021	$ 162,439
Short-term Debt \| FHLBB borrowings
Debt Instrument [Line Items]
FHLBB borrowings	0	$ 25,000
Short-term Debt \| Customer repurchase agreements
Debt Instrument [Line Items]
Securities Sold under Agreements to Repurchase	162,439	237,984
Short-term Debt \| FHLBB and correspondent bank overnight borrowings
Debt Instrument [Line Items]
FHLBB and correspondent bank overnight borrowings	0	5,825
Long-term Debt \| FHLBB borrowings
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
Long-term Federal Home Loan Bank Advances	$ 25,000	$ 10,000
Subsidiary One [Member] \| Junior Subordinated Debt
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	1.64%	3.36%
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
Thereafter	$ 36,083
Total long-term borrowings	$ 36,083	$ 36,083
Subsidiary Two [Member] \| Junior Subordinated Debt
Debt Instrument [Line Items]
Weighted Average Rate (as a percent)	1.66%	3.41%
Maturities of Long-term Debt and Capital Lease Obligations [Abstract]
Thereafter	$ 8,248
Total long-term borrowings	$ 8,248	$ 8,248

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