BORROWINGS (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repurchase Agreements	$ 256,274	$ 244,646
Total short-term borrowings	552,624	541,796
Long-term Federal Home Loan Bank Advances	10,000	10,000
Total long-term borrowings	10,773	10,791
Short-term Debt [Member]
Debt Instrument [Line Items]
Repurchase Agreements	256,274	244,646
FHLBB advances less than 90 days	135,000	250,000
FHLBB and correspondent bank overnight borrowings	161,350	47,150
Long-term Debt [Member]
Debt Instrument [Line Items]
Capital lease obligation	$ 773	$ 791