Name:	senea_IncomeTaxExpenseBenefitIncludingDiscontinuedOperations
Namespace Prefix:	senea_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Amount of current federal, state, and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current national, regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-SubTopic 10
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-9

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

Amount of current federal tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current national tax expense (benefit) for non-US (United States of America) jurisdiction.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(1)(Note 1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-SubTopic 10
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-9

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

Amount of current state and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, current regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction.

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

Amount of deferred federal tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, deferred national tax expense (benefit) for non-US (United States of America) jurisdiction.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(1)(Note 1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-9

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

Amount of deferred federal, state, and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, deferred national, regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-10

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

Amount of deferred state and local tax expense (benefit) attributable to income (loss) from continuing operations. Includes, but is not limited to, deferred regional, territorial, and provincial tax expense (benefit) for non-US (United States of America) jurisdiction.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(1)(Note 1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-9