Name:	SFST_ProvisionForCreditLosses
Namespace Prefix:	SFST_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Reserve for unfunded commitments to unfunded loan commitments percentage.

No definition available.

Name:	SFST_ReserveForUnfundedCommitmentsToUnfundedLoanCommitmentsPercentage
Namespace Prefix:	SFST_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Unfunded loan commitments are those commitments made by a Financial institution that are contractual obligations for future funding.

No definition available.

Name:	SFST_UnfundedLoanCommitments
Namespace Prefix:	SFST_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 326
-SubTopic 20
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-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

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

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

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