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Investment Securities (Details)	Mar. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Fair market value, less than 12 months, number of investments	114

X

- Definition

Number of investments in continuous unrealized loss position, less than twelve months.

+ References

No definition available.

+ Details

Name:	sfst_NumberOfInvestmentsInContinuousUnrealizedLossPositionLessThanTwelveMonths
Namespace Prefix:	sfst_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

X

- References

No definition available.

+ Details

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