BORROWED FUNDS (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Borrowings and junior subordinated debentures
Short-term borrowings	$ 894,500,000us-gaap_ShortTermBorrowings	$ 900,900,000us-gaap_ShortTermBorrowings
Long-term borrowings	151,383,000us-gaap_LongTermDebt	151,423,000us-gaap_LongTermDebt
Total borrowings	1,045,883,000us-gaap_DebtAndCapitalLeaseObligations	1,052,323,000us-gaap_DebtAndCapitalLeaseObligations
Weighted average rate on short-term borrowings (as a percent)	0.25%	0.23%
Weighted average rate on long-term borrowings (as a percent)	4.02%	4.03%
Weighted Average Rate (as a percent)	0.80%us-gaap_DebtWeightedAverageInterestRate	0.79%us-gaap_DebtWeightedAverageInterestRate
Secured line of credit	3,000,000us-gaap_LinesOfCreditCurrent
Advances from the FHLB
Borrowings and junior subordinated debentures
Short-term borrowings	884,500,000	890,900,000
Long-term borrowings	61,618,000	61,676,000
Weighted average rate on short-term borrowings (as a percent)	0.25%	0.24%
Weighted average rate on long-term borrowings (as a percent)	0.91%	0.93%
Outstanding balance on FHLBB line of credit	0	0
Advances from the FHLB, callable advances
Borrowings and junior subordinated debentures
Long-term borrowings	5,000,000	5,000,000
Advances from the FHLB, amortizing advances
Borrowings and junior subordinated debentures
Long-term borrowings	5,100,000	5,100,000
Federal Reserve Bank Advances
Borrowings and junior subordinated debentures
Short-term borrowings	0	0
Notes
Borrowings and junior subordinated debentures
Long-term borrowings	74,301,000	74,283,000
Weighted average rate on long-term borrowings (as a percent)	7.00%	7.00%
Junior subordinated debentures
Borrowings and junior subordinated debentures
Long-term borrowings	15,464,000	15,464,000
Weighted average rate on long-term borrowings (as a percent)	2.11%	2.08%
Other borrowings
Borrowings and junior subordinated debentures
Short-term borrowings	$ 10,000,000	$ 10,000,000
Weighted average rate on short-term borrowings (as a percent)	1.83%	1.80%

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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