Fair Value Accounting (Details Textual)	12 Months Ended
Dec. 31, 2020
Fair Value Disclosures [Abstract]
Percentage of loans collateralize by real estate	85% of loans

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