Long-term Borrowings (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015		Jan. 01, 2015
Debt Disclosure [Abstract]
Percentage of entity's assets equal to line of credit facility	30.00%
Collateral pledged under blanket floating lien agreement	$ 402,920,000
Long term advances with federal home loan bank [Abstract]
Advance Amount	9,974,000	$ 9,958,000	[1]
Advances due, net of fair value discount	26,000
Public deposit accounts	$ 150,467,000
MainStreet BankShares, Inc. [Member]
Long term advances with federal home loan bank [Abstract]
Long-term borrowings acquired				$ 0
Amount of loan taken to fund merger				$ 0
November 2017 [Member]
Long term advances with federal home loan bank [Abstract]
Due by	Nov. 30, 2017	Nov. 30, 2017
Advance Amount	$ 9,974,000	$ 9,958,000
November 2017 [Member] | Weighted Average [Member]
Long term advances with federal home loan bank [Abstract]
Weighted Average Rate	2.98%	2.98%
Federal Home Loan Bank Advances [Member]
Long term advances with federal home loan bank [Abstract]
Outstanding letters of credit	$ 70,000,000
US government and agency securities [Member]
Long term advances with federal home loan bank [Abstract]
Outstanding letters of credit	$ 133,297,000

[1] Derived from audited consolidated financial statements.