Note 10 - Intangible Assets by Reporting Segment (Details) - USD ($) $ in Thousands	Mar. 28, 2020	Sep. 28, 2019
Finite-lived intangible assets, accumulated amortization	$ 18,944	$ 17,691
Intangible assets	100,892	72,613
Food Service [Member]
Finite-lived intangible assets, accumulated amortization	12,594	11,846
Intangible assets	32,505	32,856
Food Service [Member] \| Noncompete Agreements [Member]
Finite-lived intangible assets, gross	670	858
Finite-lived intangible assets, accumulated amortization	561	665
Food Service [Member] \| Customer Relationships [Member]
Finite-lived intangible assets, gross	19,737	19,900
Finite-lived intangible assets, accumulated amortization	10,763	9,954
Food Service [Member] \| License and Rights [Member]
Finite-lived intangible assets, gross	1,690	1,690
Finite-lived intangible assets, accumulated amortization	1,270	1,227
Retail Supermarket [Member]
Finite-lived intangible assets, accumulated amortization	5,198	4,810
Intangible assets	21,333	21,405
Retail Supermarket [Member] \| Customer Relationships [Member]
Finite-lived intangible assets, gross	7,907	7,979
Finite-lived intangible assets, accumulated amortization	4,744	4,421
Retail Supermarket [Member] \| Finite-lived Trade Names [Member]
Finite-lived intangible assets, gross	676	676
Finite-lived intangible assets, accumulated amortization	454	389
Frozen Beverages [Member]
Finite-lived intangible assets, accumulated amortization	1,152	1,035
Intangible assets	47,054	18,352
Frozen Beverages [Member] \| Customer Relationships [Member]
Finite-lived intangible assets, gross	1,439	737
Finite-lived intangible assets, accumulated amortization	185	102
Frozen Beverages [Member] \| License and Rights [Member]
Finite-lived intangible assets, gross	1,400	1,400
Finite-lived intangible assets, accumulated amortization	967	933
Trade Names [Member] \| Food Service [Member]
Indefinite-lived intangible assets, gross	10,408	10,408
Trade Names [Member] \| Retail Supermarket [Member]
Indefinite-lived intangible assets, gross	12,750	12,750
Trade Names [Member] \| Frozen Beverages [Member]
Indefinite-lived intangible assets, gross	9,315	9,315
Distribution Rights, Indefinite-lived [Member] \| Frozen Beverages [Member]
Indefinite-lived intangible assets, gross	$ 34,900	$ 6,900

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 928
-SubTopic 340
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6473545&loc=d3e61844-108004

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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

- Definition

Amount of assets, excluding financial assets and goodwill, lacking physical substance and having a projected indefinite period of benefit.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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

- Definition

Amount before accumulated amortization of intangible assets, excluding goodwill.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jjsf_FoodServiceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_NoncompeteAgreementsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=jjsf_LicenseAndRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jjsf_RetailSupermarketMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=jjsf_FiniteLivedTradeNamesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementBusinessSegmentsAxis=jjsf_FrozenBeveragesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_TradeNamesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=jjsf_DistributionRightsIndefinitelivedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: