Document and Entity Information	6 Months Ended
	Sep. 29, 2012	Oct. 18, 2012 Common Class A Member	Oct. 18, 2012 Common Class B Member
Document And Entity Information [Abstract]
Document Type	10-Q
Document period end date	Sep. 29, 2012
Amendment flag	false
Document Period Focus	Q2
Document Fiscal Year Focus	2013
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
Class Of Stock [Line Items]
Entity common stock shares outstanding		8,687,370	2,082,282