Loans (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Dec. 31, 2015	Dec. 11, 2015
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			$ 699,703,000	$ 695,031,000
Individually evaluated for impairment			13,238,000	12,284,000
Loans acquired with deteriorated credit quality			3,483,000	3,818,000
Collectively evaluated for impairment			682,982,000	678,929,000
Allowance for loan losses			7,275,000	7,106,000
Allowance for loan losses related to individually evaluated for impairment			475,000	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			6,800,000	6,751,000
Net loans			692,428,000	687,925,000
Net loans, individually evaluated for impairment			12,763,000	11,929,000
Net loans, loans acquired with deteriorated credit quality			3,483,000	3,818,000
Net loans, collectively evaluated for impairment			676,182,000	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			475,000	355,000
Collectively evaluated for impairment			6,800,000	6,751,000
Total	$ 7,275,000	$ 6,815,000	7,275,000	7,106,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	7,106,000	6,815,000
Charge-offs	(15,000)	(25,000)
Recoveries	49,000	12,000
Provision	135,000	120,000
Balance at end of period	$ 7,275,000	6,922,000
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			201,988,000	203,407,000
Individually evaluated for impairment			523,000	304,000
Loans acquired with deteriorated credit quality			33,000	35,000
Collectively evaluated for impairment			201,432,000	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			49,000	37,000
Collectively evaluated for impairment			917,000	868,000
Total	$ 966,000	878,000	966,000	905,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	905,000	878,000
Charge-offs	0	(17,000)
Recoveries	0	0
Provision	61,000	62,000
Balance at end of period	966,000	923,000
Commercial and Agricultural Real Estate Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			299,633,000	295,364,000
Individually evaluated for impairment			6,438,000	6,235,000
Loans acquired with deteriorated credit quality			2,761,000	2,908,000
Collectively evaluated for impairment			290,434,000	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			103,000	62,000
Collectively evaluated for impairment			3,835,000	3,723,000
Total	3,938,000	3,870,000	3,938,000	3,785,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	3,785,000	3,870,000
Charge-offs	0	0
Recoveries	4,000	4,000
Provision	149,000	(175,000)
Balance at end of period	3,938,000	3,699,000
Construction [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			8,699,000	15,011,000
Individually evaluated for impairment			0	0
Loans acquired with deteriorated credit quality			0	0
Collectively evaluated for impairment			8,699,000	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			14,000	24,000
Total	14,000	26,000	14,000	24,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	24,000	26,000
Charge-offs	0	0
Recoveries	0	0
Provision	(10,000)	(15,000)
Balance at end of period	14,000	11,000
Consumer [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			11,125,000	11,543,000
Individually evaluated for impairment			0	0
Loans acquired with deteriorated credit quality			8,000	9,000
Collectively evaluated for impairment			11,117,000	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			96,000	102,000
Total	96,000	84,000	96,000	102,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	102,000	84,000
Charge-offs	(15,000)	(7,000)
Recoveries	39,000	8,000
Provision	(30,000)	(3,000)
Balance at end of period	96,000	82,000
Other Commercial and Agricultural Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			69,197,000	71,206,000
Individually evaluated for impairment			6,277,000	5,745,000
Loans acquired with deteriorated credit quality			681,000	866,000
Collectively evaluated for impairment			62,239,000	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			323,000	256,000
Collectively evaluated for impairment			1,024,000	1,049,000
Total	1,347,000	1,224,000	1,347,000	1,305,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	1,305,000	1,224,000
Charge-offs	0	(1,000)
Recoveries	6,000	0
Provision	36,000	63,000
Balance at end of period	1,347,000	1,286,000
State and Political Subdivision Loans [Member]
Segments of loan portfolio and allowance for loan losses [Abstract]
Total financing receivables			109,061,000	98,500,000
Individually evaluated for impairment			0	0
Loans acquired with deteriorated credit quality			0	0
Collectively evaluated for impairment			109,061,000	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			666,000	593,000
Total	666,000	545,000	666,000	593,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	593,000	545,000
Charge-offs	0	0
Recoveries	0	0
Provision	73,000	27,000
Balance at end of period	666,000	572,000
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			248,000	392,000
Total	392,000	188,000	248,000	392,000
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Balance at beginning of period	392,000	188,000
Charge-offs	0	0
Recoveries	0	0
Provision	(144,000)	161,000
Balance at end of period	248,000	$ 349,000
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	(637,000)		(551,000)	(637,000)	$ 665,000
Changes in the accretable yield for purchased credit-impaired loans [Roll Forward]
Balance at beginning of period	637,000
Accretion	(86,000)
Balance at end of period	$ 551,000
Loans acquired with specific evidence of deterioration in credit quality [Abstract]
Outstanding balance			6,516,000	6,950,000
Carrying amount			$ 3,483,000	$ 3,818,000