Note 4 - Loans and Allowance for Credit Losses - Loans Acquired in King Acquisition (Details) - USD ($) $ in Thousands		3 Months Ended
May 01, 2019	Mar. 31, 2019
Non-accretable amount		$ 0
King Bancorp Inc. [Member]
Contractual receivable	$ 165,744
Non-accretable amount	(1,579)
Accretable amount	(136)
Acquisition-day Fair Value	164,029
King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	164,165
Non-accretable amount	0
Accretable amount	(136)
Acquisition-day Fair Value	164,029
King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	1,579
Non-accretable amount	(1,579)
Accretable amount	0
Acquisition-day Fair Value	0
Commercial and Industrial Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	8,249
Non-accretable amount	0
Accretable amount	(23)
Acquisition-day Fair Value	8,226
Commercial and Industrial Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Acquisition-day Fair Value	0
Construction and Development [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	18,738
Non-accretable amount	0
Accretable amount	86
Acquisition-day Fair Value	18,824
Construction and Development [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	135,650
Non-accretable amount	0
Accretable amount	(126)
Acquisition-day Fair Value	135,524
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Commercial Real Estate [Member]
Contractual receivable	84,219
Non-accretable amount	0
Accretable amount	(456)
Acquisition-day Fair Value	83,763
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Residential Loans [Member]
Contractual receivable	50,556
Non-accretable amount	0
Accretable amount	322
Acquisition-day Fair Value	50,878
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member] \| Home Equity Line of Credit [Member]
Contractual receivable	875
Non-accretable amount	0
Accretable amount	8
Acquisition-day Fair Value	883
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	1,579
Non-accretable amount	(1,579)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member] \| Commercial Real Estate [Member]
Contractual receivable	1,351
Non-accretable amount	(1,351)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member] \| Residential Loans [Member]
Contractual receivable	228
Non-accretable amount	(228)
Accretable amount	0
Acquisition-day Fair Value	0
Real Estate Mortgage Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member] \| Home Equity Line of Credit [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Acquisition-day Fair Value	0
Consumer Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired and No Credit Deterioration [Member]
Contractual receivable	1,528
Non-accretable amount	0
Accretable amount	(73)
Acquisition-day Fair Value	1,455
Consumer Portfolio Segment [Member] \| King Bancorp Inc. [Member] \| Financial Asset Acquired with Credit Deterioration [Member]
Contractual receivable	0
Non-accretable amount	0
Accretable amount	0
Acquisition-day Fair Value	$ 0

The accretable amount of acquired receivables from a business combination.

No definition available.

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Namespace Prefix:	sybt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of acquired receivable from business combination, excluding certain loans and debt securities acquired in transfer.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121647850&loc=d3e4845-128472

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

For receivables acquired in a business combination, excluding certain loans and debt securities acquired in a transfer (as defined), this element represents the gross contractual amounts receivable, by major class of receivable, such as loans, direct finance leases (as defined), and any other class of receivables.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=121647850&loc=d3e4845-128472

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of reclassification (to) from nonaccretable difference (from) to the excess of a loan's cash flows expected to be collected over the investor's initial investment in acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121585399&loc=d3e13503-111538

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 15
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121585399&loc=d3e13503-111538

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=121614798&loc=d3e15032-111544

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- Details

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