DERIVATIVES - Additional Information (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($) entity	Dec. 31, 2017 USD ($) entity
Derivative [Line Items]
Maximum derivative notional position as a percentage of assets	35.00%
Maximum credit exposure as a percentage of capital	3.00%
Maximum single counterparty credit risk exposure	$ 20,000
Inerest-bearing deposit liability	$ 2,624,586	$ 1,674,080
Number of counterparties | entity	13	13
Derivative Asset	$ 33,286	$ 12,682
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	33,278	12,687
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	20,800	12,300
Other Credit Derivatives [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	20,800	15,400
Credit Risk Derivative Liabilities, at Fair Value		100
Credit Risk Contract [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	150,100	95,900
Credit Risk Derivative Liabilities, at Fair Value		100
Accrued interest and other liabilities | Derivative [Member]
Derivative [Line Items]
Inerest-bearing deposit liability	1,300,000	837,500
Derivative Asset	$ (26,000)
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		$ 1,300