Document And Entity Information - shares	9 Months Ended
	Dec. 28, 2019	Jan. 24, 2020
Document Information [Line Items]
Entity Registrant Name	Seneca Foods Corporation
Entity Central Index Key	0000088948
Trading Symbol	senea
Current Fiscal Year End Date	--03-31
Entity Filer Category	Accelerated Filer
Entity Current Reporting Status	Yes
Entity Emerging Growth Company	false
Entity Small Business	true
Entity Shell Company	false
Document Type	10-Q
Document Period End Date	Dec. 28, 2019
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Amendment Flag	false
Title of 12(b) Security	Common Stock Class A, $.25 Par Common Stock Class B, $.25 Par
Entity Interactive Data Current	Yes
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		1,735,636
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		7,418,535