Commitments and Contingent Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments and Contingent Liabilities [Abstract]
Number of banking facilities leased	4
Operating Leased Assets [Line Items]
Rent expense	$ 632,000	$ 622,000	$ 578,000
Number of data processing contractual obligations greater than one year	1
Contractual core data processing expense	1,039,000	1,012,000	895,000
Interchange processing expense	737,000	574,000
Interchange processing income	737,000	574,000
Future Minimum Lease Payments Due and Contractual Obligations [Abstract]
2013	2,408,000
2014	2,466,000
2015	2,579,000
2016	661,000
2017	651,000
Thereafter	6,259,000
Total	15,025,000
Daily average required cash balances with the Federal Reserve Bank for the final weekly reporting period	17,400,000	17,100,000
Sudley Road, Manassas Branch [Member]
Operating Leased Assets [Line Items]
Original term of lease	5 years
Number of additional options for lease extensions	1
Term of optional lease extensions	5 years
Projected rent for 2013	221,000
Old Town, Manassas [Member]
Operating Leased Assets [Line Items]
Original term of lease	5 years
Number of additional options for lease extensions	1
Term of optional lease extensions	5 years
Projected rent for 2013	48,000
Haymarket, Virginia [Member]
Operating Leased Assets [Line Items]
Original term of lease	20 years
Number of additional options for lease extensions	2
Term of optional lease extensions	5 years
Annual increase in rent (in hundredths)	3.00%
Projected rent for 2013	177,000
Bristow, Virginia [Member]
Operating Leased Assets [Line Items]
Original term of lease	10 years
Number of additional options for lease extensions	2
Term of optional lease extensions	5 years
Annual increase in rent (in hundredths)	3.00%
Projected rent for 2013	$ 192,000