Financial Instruments With Off-Balance Sheet Risk (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Variable rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 59,766	$ 56,410
Fixed rate
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	38,332	79,784
Total commitments to originate new loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	98,098	136,194
Unadvanced portion of loans and unused lines of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	1,413,737	1,327,140
Standby letters of credit
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	36,755	46,291
Forward commitments to sell loans
Supply Commitment [Line Items]
Financial instruments with off-balance sheet risks	$ 4,657	$ 16,886