Note 1 - Summary of Significant Accounting Policies (Details Textual)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Period Look-back, Quarters	32	28

Represents the number of quarters for the look-back period for the critical accounting policy related to allowance and provision for loan losses.

No definition available.

Name:	sybt_PeriodLookbackQuarters
Namespace Prefix:	sybt_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration