Summary of Significant Accounting Policies (Details)	1 Months Ended	12 Months Ended
	Jul. 31, 2011 trust	Dec. 31, 2017 USD ($) acquisition	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jan. 01, 2015 bank	Jul. 01, 2011 bank
Interest-bearing Deposits in Other Banks [Abstract]
Maturity period of interest bearing deposits in other banks		1 year
Derivative Loan Commitments [Abstract]
Derivative loan commitments income		$ 0	$ 0	$ 0
Period of time between issuance and sale of loan commitment, minimum		30 days
Period of time between issuance and sale of loan commitment, maximum		60 days
Loans [Abstract]
Period to discontinued interest accrual on delinquent loans		90 days
Past due period when loans are charged off		120 days
Substandard and doubtful risk graded loan on unsecured basis		$ 100,000
Troubled Debt Restructurings [Abstract]
Loans classified as TDR		$ 1,306,000	2,670,000
Finite-Lived Intangible Assets [Line Items]
Bank owned life insurance, number of acquisitions over the past decade | acquisition		3
Income Taxes [Abstract]
Percentage of tax benefit that is being realized for settlement (in hundredths)		50.00%
Unrecognized tax benefits		$ 0	0
Advertising and Marketing Costs [Abstract]
Advertising and marketing costs		352,000	260,000	356,000
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit attributable to ASU 2016-09			$ 17,000	$ 13,000
Reclassification of stranded tax effects from tax rate change		$ (545,000)
Franklin Community Bank
Business Acquisition [Line Items]
Number of banking offices | bank					3
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives		3 years
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible		8 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives		39 years
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible		10 years
Software
Property, Plant and Equipment [Line Items]
Estimated useful lives		3 years
MidCarolina
Finite-Lived Intangible Assets [Line Items]
Amortization period of intangible	108 months
MidCarolina | North Carolina
Business Acquisition [Line Items]
Number of branches added upon completion of acquisition | bank						8
MidCarolina | Delaware
Business Acquisition [Line Items]
Number of unconsolidated statutory trusts | trust	2
Accounting Standard Update 2018-02 | New Accounting Principles, Early Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reclassification of stranded tax effects from tax rate change		$ 545,000