ACQUISITION OF FNB, Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Integration costs and amortization of fair value [Abstract]
Net interest income		$ 9,876	$ 9,712	$ 9,171	$ 9,205	$ 8,040	$ 7,645	$ 7,561	$ 7,587	$ 37,964	$ 30,833	$ 30,338
Non-interest income		1,992	1,908	1,855	1,889	1,876	1,736	1,780	1,602	7,899	7,423	7,356
Net income		$ 3,171	$ 3,153	$ 3,031	$ 3,283	$ 2,460	$ 2,857	$ 3,189	$ 3,120	12,638	11,626	13,385
First National Bank of Fredericksburg [Member]
Integration costs and amortization of fair value [Abstract]
Net interest income	$ 401
Non-interest income	21
Net income	$ (22)
Proforma net interest income										35,837	37,736	37,634
Proforma non-interest income										7,899	8,576	8,184
Proforma net income										$ 12,073	$ 8,640	$ 14,019
Pro forma earnings per share [Abstract]
Basic (in dollars per share)										$ 3.61	$ 2.57	$ 4.15
Diluted (in dollars per share)										$ 3.61	$ 2.57	$ 4.15