LOANS AND ALLOWANCE FOR PROBABLE LOAN LOSSES - Narrative (Details) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable, Gross, Allowance, and Net [Abstract]
Loans to related parties		$ 4,000,000	$ 5,500,000
Related party loans as a percent of stockholders' equity		0.60%	0.70%
Financing Receivable, Allowance for Credit Losses [Line Items]
Impaired loans without an allowance		$ 0	$ 0
Nonaccrual loans	[1],[2]	35,770,000	2,937,000
Troubled Debt Restructurings (TDR) in Default		216,000	138,000
Commitments to lend additional funds on Troubled Debt Restructurings (TDR)		0	0
Minimum
Financing Receivable, Allowance for Credit Losses [Line Items]
Loan review larger dollar loan relationship scope, aggregate debt		500,000
Specifically reserved loans or loan relationships threshold		150,000
1-4 Family Residential Real Estate Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Nonaccrual loans		2,202,000	1,098,000
Loans for which formal foreclosure proceedings were in process		147,000	154,000
Commercial Real Estate Loans
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans secured by owner and non-owner occupied commercial real estate		1,130,000,000
Loans secured by multi-family properties		49,200,000
Loans secured by farmland		15,800,000
Nonaccrual loans		$ 32,599,000	$ 595,000

[1] Excludes PCI loans measured at fair value at acquisition if the timing and amount of cash flows expected to be collected from those sales can be reasonably estimated. The increase in nonaccrual loans was primarily due to the addition of four commercial real estate loans to nonaccrual status during the year, one of which was added during the fourth quarter.

[2] Includes $10.9 million and $1.3 million of restructured loans as of December 31, 2018 and 2017, respectively.