INCOME TAXES (Narrative) (Details) - USD ($)			3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 22, 2017	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
INCOME TAXES [Abstract]
Deferred tax assets, valuation allowance			$ 0	$ 0	$ 0
Unrecognized tax benefits				0
Unrecognized tax benefits, income tax penalties and interest expense				$ 0	$ 0	$ 0
U.S. Federal income tax rate	21.00%	21.00%		21.00%	21.00%	34.00%
Income Tax Examination, Description				Southern National and its subsidiaries file a consolidated U.S. federal income tax return, and Southern National files a Virginia state income tax return. Sonabank files a Maryland state income tax return. These returns are subject to examination by taxing authorities for all years after 2015.
Tax adjustment related to reduction in U.S. federal statutory income tax rate						$ 7,211,000
Increase (decrease) to deferred tax liabilities				$ 600,000
Increase (decrease) to deferred tax assets				$ 1,200,000
Opertaing loss carryforward write off (reversal)			$ 5,500,000