LOANS AND THE ALLOWANCE FOR LOAN LOSSES - Summary of loans (Details) - USD ($) $ in Thousands	Jun. 30, 2020	May 15, 2020	Dec. 31, 2019
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 1,424,160		$ 996,559
Deferred costs, net	(1,720)		1,448
Allowance for loan losses	(10,354)		(7,875)
Net loans	1,412,086		990,132
Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	123,800	$ 120,642
Cash, Securities and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	371,111		146,701
Cash, Securities and Other | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		13,457
Construction and Development
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	74,793		28,120
Construction and Development | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		40,407
1-4 Family Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	418,409		400,134
1-4 Family Residential | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		7,252
Non-Owner Occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	229,150		165,179
Non-Owner Occupied CRE | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		545
Owner Occupied CRE
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	117,426		127,968
Owner Occupied CRE | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		321
Commercial and Industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	213,271		$ 128,457
Commercial and Industrial | Simmons Bank
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans		$ 58,660
Paycheck Protection Program Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	204,600
Paycheck Protection Program Loan [Member] | Cash, Securities and Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total gross loans	$ 204,600
Percent of Loans on Total Loan Segment	55.10%