LOANS HELD FOR INVESTMENT AND ALLOWANCE FOR CREDIT LOSSES (Activity in the allowance for credit losses) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses	$ 4,990	$ 767
Charge-Offs		(1,361)
Recoveries		504
Net Charge-Offs		(857)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	13,905	14,210
Provision for credit losses	4,990
Charge-Offs	(2,080)
Recoveries	999
Net Charge-Offs	(1,081)
Ending Balance	21,083	14,120
Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,269
Commercial, Financial and Agricultural [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		217
Charge-Offs		(95)
Recoveries		74
Net Charge-Offs		(21)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	1,675	1,434
Provision for credit losses	406
Charge-Offs	(362)
Recoveries	40
Net Charge-Offs	(322)
Ending Balance	2,247	1,630
Commercial, Financial and Agricultural [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	488
Real Estate - Construction [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		101
Charge-Offs		0
Recoveries		0
Net Charge-Offs		0
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	370	280
Provision for credit losses	567
Charge-Offs	0
Recoveries	0
Net Charge-Offs	0
Ending Balance	1,239	381
Real Estate - Construction [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	302
Real Estate - Commercial Mortgage [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		(103)
Charge-Offs		(155)
Recoveries		70
Net Charge-Offs		(85)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,416	4,181
Provision for credit losses	774
Charge-Offs	(11)
Recoveries	191
Net Charge-Offs	180
Ending Balance	5,828	3,993
Real Estate - Commercial Mortgage [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	1,458
Real Estate - Residential [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		6
Charge-Offs		(264)
Recoveries		44
Net Charge-Offs		(220)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,128	3,400
Provision for credit losses	1,704
Charge-Offs	(110)
Recoveries	40
Net Charge-Offs	(70)
Ending Balance	6,005	3,186
Real Estate - Residential [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	1,243
Real Estate - Home Equity [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		(20)
Charge-Offs		(52)
Recoveries		32
Net Charge-Offs		(20)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	2,224	2,301
Provision for credit losses	101
Charge-Offs	(31)
Recoveries	33
Net Charge-Offs	2
Ending Balance	2,701	2,261
Real Estate - Home Equity [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	374
Consumer [Member]
Activity in the allowance for loan losses by portfolio class
Provision for Loan Losses		566
Charge-Offs		(795)
Recoveries		284
Net Charge-Offs		(511)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	3,092	2,614
Provision for credit losses	1,438
Charge-Offs	(1,566)
Recoveries	695
Net Charge-Offs	(871)
Ending Balance	3,063	$ 2,669
Consumer [Member] | Impact of Adoption of ASC 326 [Member]
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning Balance	$ (596)