FAIR VALUE - Summary of Estimated Fair Values and Carrying Amounts of Financial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Financial assets:
Cash and due from banks	$ 67,633	$ 77,693
Interest-bearing deposits with banks	422,148	39,501
Securities available for sale	537,746	638,291
Securities held to maturity	115,745	135,027
Loans held for sale	10,000	12,600
Accrued interest receivable	15,367	10,908
Carrying Amount
Financial assets:
Cash and due from banks	67,633	77,693
Interest-bearing deposits with banks	422,148	39,501
Securities available for sale	537,746	638,291
Securities restricted	28,987	32,879
Securities held to maturity	111,307	133,638
Loans held for sale	10,000	12,643	$ 12,600
Loans, net	4,577,427	3,647,499
Derivatives	62,940	15,437
Accrued interest receivable	15,367	10,908
Financial liabilities:
Certificates of deposit	297,999	307,977
Demand and other deposits	4,782,420	3,506,670
FHLB advances	340,000	435,000
Repurchase agreements	1,670	999
Subordinated debentures	78,990	78,920
Derivatives	75,281	16,645
Accrued interest payable	1,482	1,467
Fair Value
Financial assets:
Cash and due from banks	67,633	77,693
Interest-bearing deposits with banks	422,148	39,501
Securities available for sale	537,746	638,291
Securities held to maturity	115,745	135,027
Loans held for sale	10,000	12,643
Loans, net	4,628,121	3,685,770
Derivatives	62,940	15,437
Accrued interest receivable	15,367	10,908
Financial liabilities:
Certificates of deposit	301,613	308,660
Demand and other deposits	4,782,420	3,506,670
FHLB advances	351,543	434,622
Repurchase agreements	1,670	999
Subordinated debentures	88,035	81,010
Derivatives	75,281	16,645
Accrued interest payable	1,482	1,467
Quoted Prices In Active Markets for Identical Assets (Level 1)
Financial assets:
Cash and due from banks	67,633	77,693
Interest-bearing deposits with banks	422,148	39,501
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	4,782,420	3,506,670
FHLB advances	0	195,000
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	537,746	638,291
Securities held to maturity	115,745	135,027
Loans held for sale		0
Loans, net	0	0
Derivatives	62,940	15,437
Accrued interest receivable	1,854	2,181
Financial liabilities:
Certificates of deposit	301,613	308,660
Demand and other deposits	0	0
FHLB advances	351,543	239,622
Repurchase agreements	1,670	999
Subordinated debentures	88,035	81,010
Derivatives	75,281	16,645
Accrued interest payable	1,482	1,467
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	10,000	12,643
Loans, net	4,628,121	3,685,770
Derivatives	0	0
Accrued interest receivable	13,513	8,727
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