Document And Entity Information - shares	9 Months Ended
	Dec. 29, 2018	Jan. 25, 2019
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
Document Type	10-Q
Document Period End Date	Dec. 29, 2018
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Amendment Flag	false
Common Class B [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		1,874,901
Common Class A [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding (in shares)		7,700,102