LOANS, Purchased Loans (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	$ 4,776	$ 11,321
Contractual principal balance	6,728	14,784
Carrying amount, net of allowance	4,676	11,311
Increase in loan allowance related to acquisitions	90
Decrease in loan allowance related to acquisitions		70
Accretable Yield [Roll Forward]
Beginning Balance	1,208	185	$ 204
New loans purchased	0	1,151	0
Accretion of income	(249)	(128)	(19)
Income recognized upon full repayment	(205)	0	0
Reclassification from non-accretable difference	0	0	0
Disposals	0	0	0
Ending Balance	754	1,208	$ 185
Residential Real Estate [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	1,321	1,619
Commercial Real Estate [Member] | Owner Occupied [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	1,508	2,013
Commercial Real Estate [Member] | Non-Owner Occupied [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	0	5,396
Commercial and Industrial [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	211	232
Construction and Land [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	1,450	1,602
All Other [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	286	$ 459
First National Bankshares Corporation [Member] | Purchased Loans [Member]
Purchased loans [Abstract]
Loans and leases receivable purchased with deteriorated credit quality	7,286
Accretable Yield [Roll Forward]
Acquired loans contractually required payment	10,040
Acquired loans expected cash flows	$ 8,437