BORROWINGS (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Repurchase Agreements	$ 240,557	$ 230,612
Total short-term borrowings	487,355	530,129
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	240,000	210,000
FHLBB advances less than 90 days	240,557	225,605
FHLBB and correspondent bank overnight borrowings	6,730	89,450
Capital lease obligation	68	67
Long-term Debt [Member]
Debt Instrument [Line Items]
Capital lease obligation	773	791
Commercial and Industrial Sector [Member] | Short-term Debt [Member]
Debt Instrument [Line Items]
Repurchase Agreements	$ 0	$ 5,007