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Fair Value Accounting (Details Textual)	12 Months Ended
	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Percentage of loans collateralize by real estate	More than 83%

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- Definition

Percentage of company's loans collateral by real estate.

+ References

No definition available.

+ Details

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

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- References

No definition available.

+ Details

Name:	us-gaap_FairValueDisclosuresAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration