Document and Entity Information - shares	6 Months Ended
	Oct. 01, 2016	Oct. 27, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Document period end date	Oct. 01, 2016
Amendment flag	false
Document Period Focus	Q2
Document Fiscal Year Focus	2017
Current fiscal year end date	--03-31
Entity central index key	0000088948
Entity current reporting status	Yes
Entity filer category	Accelerated Filer
Entity registrant name	SENECA FOODS CORP /NY/
Entity voluntary filers	No
Entity well known seasoned issuer	No
Common Class A [Member]
Class Of Stock [Line Items]
Entity common stock shares outstanding		7,884,911
Trading Symbol	SENEA
Common Class B [Member]
Class Of Stock [Line Items]
Entity common stock shares outstanding		1,894,221
Trading Symbol	SENEB