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v3.20.4

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

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- Definition Percentage of company's loans collateral by real estate. + References No definition available. + Details
Name: | sfst_PercentageOfLoansCollateralByRealEstate
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