FAIR VALUE - Summary of Estimated Fair Values and Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financial assets:
Cash and due from banks	$ 63,687	$ 76,614
Interest earning deposits with banks	61,414	18,133
Securities available for sale	661,862	759,916
Securities held to maturity	159,244	179,885
Accrued interest receivable	11,793	11,652
Carrying Amount
Financial assets:
Cash and due from banks	63,687	76,614
Interest earning deposits with banks	61,414	18,133
Securities available for sale	661,862	759,916
Securities restricted	25,162	35,349
Securities held to maturity	164,438	180,866
Loans held for sale	1,619
Loans, net	3,165,558	3,071,045
Derivatives	9,865	4,546
Accrued interest receivable	11,793	11,652
Financial liabilities:
Certificates of deposit	328,092	222,364
Demand and other deposits	3,291,050	3,112,179
Federal funds purchased		50,000
Federal Home Loan Bank advances	265,648	501,374
Repurchase agreements	816	877
Subordinated debentures	78,746	78,641
Derivatives	3,364	1,823
Accrued interest payable	494	1,574
Fair Value.
Financial assets:
Cash and due from banks	63,687	76,614
Interest earning deposits with banks	61,414	18,133
Securities available for sale	661,862	759,916
Securities held to maturity	159,244	179,885
Loans held for sale	1,692
Loans, net	3,126,345	3,010,023
Derivatives	9,865	4,546
Accrued interest receivable	11,793	11,652
Financial liabilities:
Certificates of deposit	325,354	220,775
Demand and other deposits	3,291,050	3,112,179
Federal funds purchased		50,000
Federal Home Loan Bank advances	259,116	498,558
Repurchase agreements	816	877
Subordinated debentures	73,917	77,933
Derivatives	3,364	1,823
Accrued interest payable	494	1,574
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and due from banks	63,687	76,614
Interest earning deposits with banks	61,414	18,133
Securities available for sale	0	0
Securities held to maturity	0	0
Loans held for sale	0
Loans, net	0	0
Derivatives	0	0
Accrued interest receivable	0	0
Financial liabilities:
Certificates of deposit	0	0
Demand and other deposits	3,291,050	3,112,179
Federal funds purchased		50,000
Federal Home Loan Bank advances	0	185,000
Repurchase agreements	0	0
Subordinated debentures	0	0
Derivatives	0	0
Accrued interest payable	0	0
Significant Other Observable Inputs (Level 2)
Financial assets:
Cash and due from banks	0	0
Interest earning deposits with banks	0	0
Securities available for sale	661,862	759,916
Securities held to maturity	159,244	179,885
Loans held for sale	1,692
Loans, net	0	0
Derivatives	9,865	4,546
Accrued interest receivable	2,885	3,211
Financial liabilities:
Certificates of deposit	325,354	220,775
Demand and other deposits	0	0
Federal funds purchased		0
Federal Home Loan Bank advances	259,116	313,558
Repurchase agreements	816	877
Subordinated debentures	73,917	77,933
Derivatives	3,364	1,823
Accrued interest payable	494	1,574
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and due from banks	0	0
Interest earning deposits with banks	0	0
Securities available for sale	0	0
Securities held to maturity	0	0
Loans held for sale	0
Loans, net	3,126,345	3,010,023
Derivatives	0	0
Accrued interest receivable	8,908	8,441
Financial liabilities:
Certificates of deposit	0	0
Demand and other deposits	0	0
Federal funds purchased		0
Federal Home Loan Bank advances	0	0
Repurchase agreements	0	0
Subordinated debentures	0	0
Derivatives	0	0
Accrued interest payable	$ 0	$ 0