OTHER BORROWINGS - Schedule of Other Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Subordinated deferrable interest debentures, net	$ 124,345	$ 127,560
Other borrowings	425,155	$ 1,398,709
Fixed Rate Advance due January 10, 2020; fixed interest rate of 1.68%
Debt Instrument [Line Items]
Effective interest rate		1.68%
Advance from correspondent bank	0	$ 50,000
Fixed Rate Advance due January 13, 2020; fixed interest rate of 1.68%
Debt Instrument [Line Items]
Effective interest rate		1.68%
Advance from correspondent bank	0	$ 50,000
Fixed Rate Advance due January 13, 2020; fixed interest rate of 1.67%
Debt Instrument [Line Items]
Effective interest rate		1.67%
Advance from correspondent bank	0	$ 100,000
Fixed Rate Advance due January 15, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 50,000
Fixed Rate Advance due January 16, 2020; fixed interest rate of 1.69%
Debt Instrument [Line Items]
Effective interest rate		1.69%
Advance from correspondent bank	0	$ 150,000
Fixed Rate Advance due January 17, 2020; fixed interest rate of 1.70%
Debt Instrument [Line Items]
Effective interest rate		1.70%
Advance from correspondent bank	0	$ 100,000
Fixed Rate Advance due January 21, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 50,000
Fixed Rate Advance due January 21, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 200,000
Fixed Rate Advance due January 21, 2020; fixed interest rate of 1.70%
Debt Instrument [Line Items]
Effective interest rate		1.70%
Advance from correspondent bank	0	$ 25,000
Fixed Rate Advance due January 21, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 75,000
Fixed Rate Advance due January 21, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 25,000
Fixed Rate Advance due January 23, 2020; fixed interest rate of 1.71%
Debt Instrument [Line Items]
Effective interest rate		1.71%
Advance from correspondent bank	0	$ 100,000
Fixed Rate Advance due January 27, 2020; fixed interest rate of 1.73%
Debt Instrument [Line Items]
Effective interest rate		1.73%
Advance from correspondent bank	0	$ 50,000
Fixed Rate Advance due February 18, 2020; fixed interest rate of 1.72%
Debt Instrument [Line Items]
Effective interest rate		1.72%
Advance from correspondent bank	$ 0	$ 100,000
Fixed Rate Advance due March 3, 2025; fixed interest rate of 1.208%
Debt Instrument [Line Items]
Effective interest rate	1.208%
Advance from correspondent bank	$ 15,000	0
Fixed Rate Advance due March 2, 2027; fixed interest rate of 1.445%
Debt Instrument [Line Items]
Effective interest rate	1.445%
Advance from correspondent bank	$ 15,000	0
Fixed Rate Advance due March 4, 2030; fixed interest rate of 1.606%
Debt Instrument [Line Items]
Effective interest rate	1.606%
Advance from correspondent bank	$ 15,000	0
Fixed Rate Advance due December 9, 2030; fixed interest rate of 4.55%
Debt Instrument [Line Items]
Effective interest rate	4.55%
Advance from correspondent bank	$ 1,411	1,422
Fixed Rate Advance due December 9, 2030; fixed interest rate of 4.55%
Debt Instrument [Line Items]
Effective interest rate	4.55%
Advance from correspondent bank	$ 977	985
Principal Reducing Advance due September 29, 2031; fixed interest rate of 3.095%
Debt Instrument [Line Items]
Effective interest rate	3.095%
Advance from correspondent bank	$ 1,567	1,712
Subordinated notes payable due March 15, 2027 net of unamortized debt issuance cost of $812 and $943, respectively; fixed interest rate of 5.75% through March 14, 2022; variable interest rate thereafter at three-month LIBOR plus 3.616%
Debt Instrument [Line Items]
Effective interest rate	5.75%
Subordinated deferrable interest debentures, net	$ 74,188	74,057
Unamortized debt issuance expense	$ 812	943
Subordinated notes payable due December 15, 2029 net of unamortized debt issuance cost of $2,165 and $2,408, respectively; fixed interest rate of 4.25% through December 14, 2024; variable interest rate thereafter at three-month SOFR plus 2.94%
Debt Instrument [Line Items]
Effective interest rate	4.25%
Subordinated deferrable interest debentures, net	$ 117,835	117,592
Unamortized debt issuance expense	$ 2,165	2,408
Subordinated notes payable due May 31, 2030 net of unaccreted purchase accounting fair value adjustment of $1,150 and $1,596, respectively; fixed interest rate of 5.875% through May 31, 2025; variable interest rate thereafter at three-month LIBOR plus 3.63%
Debt Instrument [Line Items]
Effective interest rate	5.875%
Subordinated deferrable interest debentures, net	$ 76,150	76,595
Unaccreted portion of fair value adjustment net	$ (1,150)	(1,596)
Subordinated notes payable due October 1, 2030 net of unamortized debt issuance cost of $1,973 and $0, respectively; fixed interest rate of 3.875% through September 30, 2025; variable interest rate thereafter at three-month SOFR plus 3.753%
Debt Instrument [Line Items]
Effective interest rate	3.875%
Subordinated deferrable interest debentures, net	$ 108,027	0
Unamortized debt issuance expense	$ 1,973	0
Advance from correspondent bank due September 5, 2026; secured by a loan receivable; fixed interest rate of 2.09%
Debt Instrument [Line Items]
Effective interest rate	2.09%
Other borrowings	$ 0	$ 1,346
London Interbank Offered Rate (LIBOR) | Subordinated notes payable due March 15, 2027 net of unamortized debt issuance cost of $812 and $943, respectively; fixed interest rate of 5.75% through March 14, 2022; variable interest rate thereafter at three-month LIBOR plus 3.616%
Debt Instrument [Line Items]
Basis spread on variable rate	3.616%
London Interbank Offered Rate (LIBOR) | Subordinated notes payable due May 31, 2030 net of unaccreted purchase accounting fair value adjustment of $1,150 and $1,596, respectively; fixed interest rate of 5.875% through May 31, 2025; variable interest rate thereafter at three-month LIBOR plus 3.63%
Debt Instrument [Line Items]
Basis spread on variable rate	3.63%
London Interbank Offered Rate (LIBOR) | Subordinated notes payable due October 1, 2030 net of unamortized debt issuance cost of $1,973 and $0, respectively; fixed interest rate of 3.875% through September 30, 2025; variable interest rate thereafter at three-month SOFR plus 3.753%
Debt Instrument [Line Items]
Basis spread on variable rate	3.753%
Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate | Subordinated notes payable due December 15, 2029 net of unamortized debt issuance cost of $2,165 and $2,408, respectively; fixed interest rate of 4.25% through December 14, 2024; variable interest rate thereafter at three-month SOFR plus 2.94%
Debt Instrument [Line Items]
Basis spread on variable rate	2.94%