Acquisition of MainStreet - Unaudited Pro Forma (Details) - MainStreet BankShares, Inc. - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Business Acquisition [Line Items]
Net interest income	$ 12,378	$ 12,512	$ 37,584	$ 37,302
Provision for loan loss	0	0	(700)	(150)
Non-interest income	3,055	3,205	9,469	9,055
Non-interest expense and income taxes	(11,245)	(11,868)	(35,660)	(34,644)
Net income	$ 4,188	$ 3,849	$ 10,693	$ 11,563