Investment Securities (Details Narrative)	Sep. 30, 2023 Integer
Investments, Debt and Equity Securities [Abstract]
Fair market value, less than 12 months, number of investments	122

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

No definition available.

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