LOANS AND ALLOWANCE FOR LOAN LOSSES - Summary of Information Pertaining to Impaired Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	$ 75,124		$ 76,457
Total impaired loans	104,733
Impaired Loans Excluding Purchased Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Nonaccrual loans	75,124	$ 42,058
Troubled debt restructurings not included above	29,609	28,063
Total impaired loans	104,733	70,121
Interest income recognized on impaired loans	4,131	3,030
Foregone interest income on impaired loans	$ 4,100	$ 2,336