Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Thousands	1 Months Ended		12 Months Ended
	Jul. 31, 2011	Apr. 30, 2006	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense			$ 528	$ 964	$ 1,201
Community First
Acquired Finite-Lived Intangible Assets [Line Items]
Core deposit intangible		$ 3,112
Amortization period of intangible		99 months
MidCarolina
Acquired Finite-Lived Intangible Assets [Line Items]
Core deposit intangible	$ 6,556
Amortization period of intangible	108 months
MainStreet BankShares, Inc.
Acquired Finite-Lived Intangible Assets [Line Items]
Core deposit intangible			$ 1,839
Amortization period of intangible			120 months