Borrowings Narrative (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Line of Credit Facility [Line Items]
Remaining credit availability	$ 291,600,000
Long-term debt	$ 85,000,000
Federal Home Loan Bank advances, Interest rate, range from (in hundredths)	0.40%
Federal Home Loan Bank advances, Interest rate, range to (in hundredths)	1.11%
Federal Home Loan Bank advances, Weighted-average rate (in hundredths)	0.66%	0.46%
Federal Home Loan Bank borrowings	$ 85,000,000	$ 55,000,000
Securities sold under agreements to repurchase, maturing the day following the day sold	26,900,000	26,300,000
Federal Reserve Bank of Richmond [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum credit limit	43,400,000.0
Revolving lines of credit, outstanding balance	0
Other Institutions [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum credit limit	35,000,000
Southern Trust Mortgage [Member] | Subsidiary Bank [Member] | Fund Mortgage Held For Sale [Member]
Line of Credit Facility [Line Items]
Line of credit, maximum credit limit	17,000,000
Revolving lines of credit, outstanding balance		$ 8,500,000
Counterparty One [Member]
Line of Credit Facility [Line Items]
Securities sold under agreements to repurchase, structured repurchase agreements, January 18, 2015	7,200,000
Counterparty Two [Member]
Line of Credit Facility [Line Items]
Securities sold under agreements to repurchase, structured repurchase agreements, January 18, 2015	$ 5,000,000