FAIR VALUE - Summary of Estimated Fair Values and Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Financial assets:
Cash and due from banks	$ 77,693	$ 142,145
Interest-bearing deposits with banks	39,501	153,223
Securities available for sale	638,291	680,886
Securities held to maturity	135,027	156,792
Accrued interest receivable	10,908	11,236
Financial liabilities:
Certificates of deposit	307,977
Carrying Amount
Financial assets:
Cash and due from banks	77,693	142,145
Interest-bearing deposits with banks	39,501	153,223
Securities available for sale	638,291	680,886
Securities restricted	32,879	24,028
Securities held to maturity	133,638	160,163
Loans held for sale	12,643
Loans, net	3,647,499	3,244,393
Derivatives	15,437	6,363
Accrued interest receivable	10,908	11,236
Financial liabilities:
Certificates of deposit	307,977	329,491
Demand and other deposits	3,506,670	3,556,902
FHLB advances	435,000	240,433
Repurchase agreements	999	539
Subordinated debentures	78,920	78,781
Derivatives	16,645	2,215
Accrued interest payable	1,467	1,524
Fair Value
Financial assets:
Cash and due from banks	77,693	142,145
Interest-bearing deposits with banks	39,501	153,223
Securities available for sale	638,291	680,886
Securities held to maturity	135,027	156,792
Loans held for sale	12,643
Loans, net	3,685,770	3,216,204
Derivatives	15,437	6,363
Accrued interest receivable	10,908	11,236
Financial liabilities:
Certificates of deposit	308,660	326,865
Demand and other deposits	3,506,670	3,556,902
FHLB advances	434,622	236,209
Repurchase agreements	999	539
Subordinated debentures	81,010	74,400
Derivatives	16,645	2,215
Accrued interest payable	1,467	1,524
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and due from banks	77,693	142,145
Interest-bearing deposits with banks	39,501	153,223
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	3,506,670	3,556,902
FHLB advances	195,000	0
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	638,291	680,886
Securities held to maturity	135,027	156,792
Loans, net	0	0
Derivatives	15,437	6,363
Accrued interest receivable	2,181	2,936
Financial liabilities:
Certificates of deposit	308,660	326,865
Demand and other deposits	0	0
FHLB advances	239,622	236,209
Repurchase agreements	999	539
Subordinated debentures	81,010	74,400
Derivatives	16,645	2,215
Accrued interest payable	1,467	1,524
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 held for sale	12,643
Loans, net	3,685,770	3,216,204
Derivatives	0	0
Accrued interest receivable	8,727	8,300
Financial liabilities:
Certificates of deposit	0	0
Demand and other deposits	0	0
FHLB advances	0	0
Repurchase agreements	0	0
Subordinated debentures	0	0
Derivatives	0	0
Accrued interest payable	$ 0	$ 0