LOANS AND ALLOWANCE FOR CREDIT LOSSES - Summary of Troubled Debt Restructuring (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2021 USD ($) contract	Mar. 31, 2020 contract	Dec. 31, 2020 USD ($) contract
Financing Receivable, Modifications [Line Items]
Total	$ 9,685		$ 9,716
Specific reserves on TDRs	$ 0		$ 0
Troubled Debt Restructurings:
Number of Contracts \| contract	1	0	4
Pre-Modification Outstanding Recorded Investment	$ 17		$ 2,435
Post-Modification Outstanding Recorded Investment	$ 17		$ 1,836
Commercial and industrial
Troubled Debt Restructurings:
Number of Contracts \| contract	1		1
Pre-Modification Outstanding Recorded Investment	$ 17		$ 129
Post-Modification Outstanding Recorded Investment	17		$ 85
Construction and development
Troubled Debt Restructurings:
Number of Contracts \| contract			2
Pre-Modification Outstanding Recorded Investment			$ 1,289
Post-Modification Outstanding Recorded Investment			$ 1,081
Commercial real estate
Troubled Debt Restructurings:
Number of Contracts \| contract			1
Pre-Modification Outstanding Recorded Investment			$ 1,017
Post-Modification Outstanding Recorded Investment			670
Nonaccrual TDRs
Financing Receivable, Modifications [Line Items]
Total	87		90
Performing TDRs
Financing Receivable, Modifications [Line Items]
Total	$ 9,598		$ 9,626

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Amount, after troubled debt restructuring, of modified financing receivable.

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Amount, before troubled debt restructuring, of financing receivable to be modified.

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Amount of financing receivable modified as troubled debt restructuring.

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