Name:	jjsf_MarketableSecuritiesAnnualIncomePercentage
Namespace Prefix:	jjsf_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

The percentage of annual income percentage from debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale that is not subject to tax.

No definition available.

Name:	jjsf_MarketableSecuritiesAnnualIncomePercentageNotSubjectToTax
Namespace Prefix:	jjsf_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

No definition available.

Name:	us-gaap_MarketableSecuritiesGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Amount of unrealized gain (loss) on investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483621/220-10-S99-2

Name:	us-gaap_MarketableSecuritiesUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

No definition available.