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Document and Entity Information - USD ($)
 12 Months Ended
Mar. 31, 2016
Jun. 03, 2016
Oct. 01, 2015
Document And Entity Information [Abstract]      
Document Type 10-K    
Document period end date Mar. 31, 2016    
Amendment flag false    
Document Period Focus FY    
Document Fiscal Year Focus 2016    
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]      
Trading Symbol SENEA    
Entity public float     $ 191,810,000
Common Class A Member      
Class Of Stock [Line Items]      
Entity common stock shares outstanding   7,918,069  
Common Class B Member      
Class Of Stock [Line Items]      
Entity common stock shares outstanding   1,894,599