Fair Value Accounting (Details Textual)	9 Months Ended
Sep. 30, 2017
Fair Value Accounting (Textual)
Percentage of loans collateralize by real estate, description	More than 80%

Percentage of company's loans collateral by real estate.

No definition available.

Name:	sfst_PercentageOfLoansCollateralByRealEstate
Namespace Prefix:	sfst_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration