Note 12 - Defined Benefit Plan (Details Textual)	9 Months Ended
Sep. 30, 2018
Defined Benefit Plan, Number of Employees Covered	3
Defined Benefit Plan, Number of Present Employees Covered	2
Defined Benefit Plan, Number of Retired Employees Covered	1
Deferred Compensation Arrangement with Individual, Requisite Service Period	25 years

Number of employees eligible to participate in the defined benefit plan or plans described.

No definition available.

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Namespace Prefix:	sybt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of present employees eligible to participate in the defined benefit plan or plans described.

+ References

No definition available.

+ Details

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Namespace Prefix:	sybt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of retired employees eligible to participate in the defined benefit plan or plans described.

+ References

No definition available.

+ Details

Name:	sybt_DefinedBenefitPlanNumberOfRetiredEmployeesCovered
Namespace Prefix:	sybt_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum period the individual is required to perform services to be fully vested under the deferred compensation arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 710
-SubTopic 10
-Section 55
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=6409961&loc=d3e20487-108367

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration