DERIVATIVES - Summary of Derivative Financial Instruments and Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	$ 1,422,978	$ 1,354,056
Estimate Fair Value Gain	12,701	12,559
Estimate Fair Value Loss	(12,703)	(12,587)
Other Credit Derivatives [Member]
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	25,500	17,800
Credit Risk Derivative Liabilities, at Fair Value	100	200
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other liabilities
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	711,489	677,028
Estimate Fair Value Gain	3,611	4,158
Estimate Fair Value Loss	(9,092)	(8,429)
Fair Value Hedges | Matched interest rate swaps | Accrued interest and other assets
Derivatives, Fair Value [Line Items]
Inerest-bearing deposit liability	711,489	677,028
Estimate Fair Value Gain	9,090	8,401
Estimate Fair Value Loss	$ (3,611)	$ (4,158)