FAIR VALUE - Summary of Estimated Fair Values and Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Financial assets:
Cash and due from banks	$ 142,145	$ 76,614
Interest-bearing deposits with banks	153,223	18,133
Securities available for sale	680,886	759,916
Securities held to maturity	156,792	179,885
Accrued interest receivable	11,236	11,652
Financial liabilities:
Certificates of deposit	329,491
Carrying Amount
Financial assets:
Cash and due from banks	142,145	76,614
Interest-bearing deposits with banks	153,223	18,133
Securities available for sale	680,886	759,916
Securities restricted	24,028	35,349
Securities held to maturity	160,163	180,866
Loans, net	3,244,393	3,071,045
Derivatives	6,363	4,546
Accrued interest receivable	11,236	11,652
Financial liabilities:
Certificates of deposit	329,491	222,364
Demand and other deposits	3,556,902	3,112,179
Federal funds purchased		50,000
FHLB advances	240,433	501,374
Repurchase agreements	539	877
Subordinated debentures	78,781	78,641
Derivatives	2,215	1,823
Accrued interest payable	1,524	1,574
Fair Value
Financial assets:
Cash and due from banks	142,145	76,614
Interest-bearing deposits with banks	153,223	18,133
Securities available for sale	680,886	759,916
Securities held to maturity	156,792	179,885
Loans, net	3,216,204	3,010,023
Derivatives	6,363	4,546
Accrued interest receivable	11,236	11,652
Financial liabilities:
Certificates of deposit	326,865	220,775
Demand and other deposits	3,556,902	3,112,179
Federal funds purchased		50,000
FHLB advances	236,209	498,558
Repurchase agreements	539	877
Subordinated debentures	74,400	77,933
Derivatives	2,215	1,823
Accrued interest payable	1,524	1,574
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and due from banks	142,145	76,614
Interest-bearing deposits with banks	153,223	18,133
Securities available for sale	0	0
Securities held to maturity	0	0
Loans, net	0	0
Derivatives	0	0
Accrued interest receivable	0	0
Financial liabilities:
Certificates of deposit	0	0
Demand and other deposits	3,556,902	3,112,179
Federal funds purchased		50,000
FHLB 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-bearing deposits with banks	0	0
Securities available for sale	680,886	759,916
Securities held to maturity	156,792	179,885
Loans, net	0	0
Derivatives	6,363	4,546
Accrued interest receivable	2,936	3,211
Financial liabilities:
Certificates of deposit	326,865	220,775
Demand and other deposits	0	0
Federal funds purchased		0
FHLB advances	236,209	313,558
Repurchase agreements	539	877
Subordinated debentures	74,400	77,933
Derivatives	2,215	1,823
Accrued interest payable	1,524	1,574
Significant Unobservable Inputs (Level 3)
Financial assets:
Cash and due from banks	0	0
Interest-bearing deposits with banks	0	0
Securities available for sale	0	0
Securities held to maturity	0	0
Loans, net	3,216,204	3,010,023
Derivatives	0	0
Accrued interest receivable	8,300	8,441
Financial liabilities:
Certificates of deposit	0	0
Demand and other deposits	0	0
Federal funds purchased		0
FHLB advances	0	0
Repurchase agreements	0	0
Subordinated debentures	0	0
Derivatives	0	0
Accrued interest payable	$ 0	$ 0