Financial Instruments With Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Variable rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 60,473	$ 59,766
Fixed rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	63,747	38,332
Total commitments to originate new loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	124,220	98,098
Unadvanced portion of loans and unused lines of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	1,468,782	1,413,737
Standby letters of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	49,117	36,755
Forward commitments to sell loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 11,850	$ 4,657