Document and Entity Information	9 Months Ended
	Dec. 31, 2011	Jan. 20, 2012 Common Class A Member	Jan. 20, 2012 Common Class B Member
Document And Entity Information [Abstract]
Document Type	10-Q
Document period end date	Dec. 31, 2011
Amendment flag	false
Document Period Focus	Q3
Document Fiscal Year Focus	2012
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		9,594,533	2,120,712