BORROWINGS (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Repurchase Agreements	$ 278,787	$ 244,646
Total short-term borrowings	409,732	541,796
Long-term Federal Home Loan Bank Advances	10,000	10,000
Total long-term borrowings	10,738	10,791
Short-term Debt [Member]
Debt Instrument [Line Items]
Repurchase Agreements	278,787	244,646
FHLBB advances less than 90 days	75,000	250,000
FHLBB and correspondent bank overnight borrowings	55,945	47,150
Long-term Debt [Member]
Debt Instrument [Line Items]
Capital lease obligation	$ 738	$ 791