TIME DEPOSITS AND SHORT-TERM DEBT (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Certificates of deposits and other time deposits over $100,000 outstanding	$ 910,200	$ 948,100
Interest expense relating to certificate and other time deposits of $100,000 or more	8,700	11,400	$ 16,000
Maturities of time deposits [Abstract]
2017	263,873
2018	151,366
2019	156,553
2020	198,309
2021	2,082
Total	772,183
End of Period Balance	467,937	391,666	421,028
Daily Average Balance	471,360	444,230	418,119
Maximum Outstanding at any Month End	807,607	582,663	473,753
Lines of credit with other banks	825,000
Federal Funds Purchased [Member]
Maturities of time deposits [Abstract]
Daily Average Balance	$ 10,066	$ 4,247	$ 1,238
Daily Average Interest Rate (in hundredths)	0.17%	0.18%	0.33%
Maximum Outstanding at any Month End	$ 25,000	$ 10,000
Period from date of sale that securities generally mature	30 days
Securities Sold Under Agreements to Repurchase [Member]
Maturities of time deposits [Abstract]
End of Period Balance	$ 405,937	$ 388,166	$ 421,028
End of Period Interest Rate (in hundredths)	0.12%	0.08%	0.07%
Daily Average Balance	$ 416,172	$ 436,875	$ 416,881
Daily Average Interest Rate (in hundredths)	0.09%	0.07%	0.07%
Maximum Outstanding at any Month End	$ 558,107	$ 569,163	$ 473,753
Federal Reserve Bank Advances [Member]
Maturities of time deposits [Abstract]
Period from date of purchase that borrowings generally mature	90 days
Federal Home Loan Bank [Member]
Maturities of time deposits [Abstract]
End of Period Balance	$ 62,000	3,500
End of Period Interest Rate (in hundredths)	0.31%
Daily Average Balance	$ 45,122	$ 3,108
Daily Average Interest Rate (in hundredths)	0.37%	2.60%
Maximum Outstanding at any Month End	$ 224,500	$ 3,500
Period from date of purchase that borrowings generally mature	30 days