Note 10 - Recent Accounting Pronouncements (Details Textual)	9 Months Ended
Sep. 30, 2020
Increase in Allowance for Loan Losses, Percent	5.00%

The percent increase in allowance for loan losses.

No definition available.

Name:	sfbs_IncreaseInAllowanceForLoanLossesPercent
Namespace Prefix:	sfbs_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration