Loans (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015	Dec. 11, 2015
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					$ 751,293,000	$ 695,031,000
Individually evaluated for impairment					11,964,000	12,284,000
Loans acquired with deteriorated credit quality					3,565,000	3,818,000
Collectively evaluated for impairment					735,764,000	678,929,000
Allowance for loan losses					8,194,000	7,106,000
Allowance for loan losses related to individually evaluated for impairment					482,000	355,000
Allowance for loan losses related to loans acquired with deteriorated credit quality					0	0
Allowance for loan losses related to collectively evaluated for impairment					7,712,000	6,751,000
Net loans					743,099,000	687,925,000
Net loans, individually evaluated for impairment					11,482,000	11,929,000
Net loans, loans acquired with deteriorated credit quality					3,565,000	3,818,000
Net loans, collectively evaluated for impairment					728,052,000	672,178,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					482,000	355,000
Collectively evaluated for impairment					7,712,000	6,751,000
Total	$ 8,194,000	$ 6,959,000	$ 7,106,000	$ 6,815,000	8,194,000	7,106,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	7,359,000	6,959,000	7,106,000	6,815,000
Charge-offs	(173,000)	(51,000)	(272,000)	(166,000)
Recoveries	508,000	17,000	590,000	36,000
Provision	500,000	120,000	770,000	360,000
Balance at end of period	8,194,000	7,045,000	$ 8,194,000	7,045,000
Minimum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Number of days past for loan to be considered impaired, Minimum			90 days
First Mortgage [Member] | Minimum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate			15 years
First Mortgage [Member] | Maximum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate			30 years
Second Mortgage [Member] | Maximum [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Period of mortgage on real estate			15 years
Residential Real Estate Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					205,092,000	203,407,000
Individually evaluated for impairment					969,000	304,000
Loans acquired with deteriorated credit quality					35,000	35,000
Collectively evaluated for impairment					204,088,000	203,068,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					39,000	37,000
Collectively evaluated for impairment					974,000	868,000
Total	1,013,000	931,000	$ 1,013,000	878,000	1,013,000	905,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	990,000	931,000	905,000	878,000
Charge-offs	(9,000)	0	(52,000)	(34,000)
Recoveries	0	0	0	0
Provision	32,000	(18,000)	160,000	69,000
Balance at end of period	1,013,000	913,000	1,013,000	913,000
Commercial and Agricultural Real Estate Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					339,704,000	295,364,000
Individually evaluated for impairment					5,567,000	6,235,000
Loans acquired with deteriorated credit quality					2,748,000	2,908,000
Collectively evaluated for impairment					331,389,000	286,221,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					46,000	62,000
Collectively evaluated for impairment					4,560,000	3,723,000
Total	4,606,000	3,679,000	3,785,000	3,870,000	4,606,000	3,785,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	3,919,000	3,679,000	3,785,000	3,870,000
Charge-offs	(100,000)	0	(100,000)	(56,000)
Recoveries	467,000	4,000	475,000	11,000
Provision	320,000	120,000	446,000	(22,000)
Balance at end of period	4,606,000	3,803,000	4,606,000	3,803,000
Construction Real Estate Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					18,774,000	15,011,000
Individually evaluated for impairment					0	0
Loans acquired with deteriorated credit quality					0	0
Collectively evaluated for impairment					18,774,000	15,011,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					34,000	24,000
Total	34,000	14,000	34,000	26,000	34,000	24,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	18,000	14,000	24,000	26,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	16,000	3,000	10,000	(9,000)
Balance at end of period	34,000	17,000	34,000	17,000
Consumer [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					11,226,000	11,543,000
Individually evaluated for impairment					0	0
Loans acquired with deteriorated credit quality					4,000	9,000
Collectively evaluated for impairment					11,222,000	11,534,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					109,000	102,000
Total	109,000	89,000	109,000	84,000	109,000	102,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	104,000	89,000	102,000	84,000
Charge-offs	(27,000)	(11,000)	(65,000)	(35,000)
Recoveries	16,000	13,000	84,000	25,000
Provision	16,000	0	(12,000)	17,000
Balance at end of period	109,000	91,000	109,000	91,000
Other Commercial and Agricultural Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					78,258,000	71,206,000
Individually evaluated for impairment					5,428,000	5,745,000
Loans acquired with deteriorated credit quality					778,000	866,000
Collectively evaluated for impairment					72,052,000	64,595,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					397,000	256,000
Collectively evaluated for impairment					1,245,000	1,049,000
Total	1,642,000	1,502,000	1,642,000	1,224,000	1,642,000	1,305,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,564,000	1,502,000	1,305,000	1,224,000
Charge-offs	(37,000)	(40,000)	(55,000)	(41,000)
Recoveries	25,000	0	31,000	0
Provision	90,000	(17,000)	361,000	262,000
Balance at end of period	1,642,000	1,445,000	1,642,000	1,445,000
State and Political Subdivision Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables					98,239,000	98,500,000
Individually evaluated for impairment					0	0
Loans acquired with deteriorated credit quality					0	0
Collectively evaluated for impairment					98,239,000	98,500,000
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					771,000	593,000
Total	771,000	568,000	771,000	545,000	771,000	593,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	764,000	568,000	593,000	545,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	7,000	18,000	178,000	41,000
Balance at end of period	771,000	586,000	771,000	586,000
Unallocated [Member]
Summary of allowance for loan losses into amount required for loans individually evaluated for impairment and the amount required for loans collectively evaluated for impairment [Abstract]
Individually evaluated for impairment					0	0
Collectively evaluated for impairment					19,000	392,000
Total	19,000	176,000	19,000	188,000	19,000	392,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	0	176,000	392,000	188,000
Charge-offs	0	0	0	0
Recoveries	0	0	0	0
Provision	19,000	14,000	(373,000)	2,000
Balance at end of period	19,000	$ 190,000	19,000	$ 190,000
First National Bank of Fredericksburg [Member]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities Acquired During Period [Line Items]
Unpaid principal balance amount							$ 6,969,000
Estimated fair value							3,809,000
Contractually required principal and interest at acquisition							9,913,000
Expected cash flows							4,474,000
Non-accretable discount							5,439,000
Accretable discount	464,000		637,000		376,000	637,000	$ 665,000
Changes in the accretable yield for purchased credit-impaired loans [Roll Forward]
Balance at beginning of period	464,000		637,000
Accretion	(88,000)		(261,000)
Balance at end of period	$ 376,000		$ 376,000
Loans acquired with specific evidence of deterioration in credit quality [Abstract]
Outstanding balance					6,774,000	6,950,000
Carrying amount					$ 3,565,000	$ 3,818,000