LOANS AND ALLOWANCE FOR CREDIT LOSSES - Troubled debt restructurings ("TDRs") (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) contract	Dec. 31, 2020 USD ($)
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	73
Financing Receivable, Troubled Debt Restructuring	$ 4,010	$ 3,321
Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 18	20
One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	19
Financing Receivable, Troubled Debt Restructuring	$ 1,648	1,899
Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	2
Financing Receivable, Troubled Debt Restructuring	$ 1,856	646
Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 67	127
Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	50
Financing Receivable, Troubled Debt Restructuring	$ 421	629
Accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	39
Financing Receivable, Troubled Debt Restructuring	$ 2,506
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		2,350
Accruing | Construction and land development
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 18
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		20
Accruing | One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	6
Financing Receivable, Troubled Debt Restructuring	$ 382
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		1,121
Accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 1,768
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		646
Accruing | Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		52
Accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	31
Financing Receivable, Troubled Debt Restructuring	$ 338
Financing Receivable, Troubled Debt Restructuring, Accruing Interest		511
Non-accruing
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	34
Financing Receivable, Troubled Debt Restructuring	$ 1,504	971
Non-accruing | One- to four-family residential construction
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	13
Financing Receivable, Troubled Debt Restructuring	$ 1,266	778
Non-accruing | Commercial Real Estate
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 88
Non-accruing | Commercial business
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	1
Financing Receivable, Troubled Debt Restructuring	$ 67	75
Non-accruing | Consumer
Financing Receivable, Troubled Debt Restructuring [Line Items]
Financing Receivable, Modifications, Number of Contracts | contract	19
Financing Receivable, Troubled Debt Restructuring	$ 83	$ 118