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Basis of Presentation (detail) (USD $)
3 Months Ended 9 Months Ended
Dec. 27, 2014
Dec. 28, 2013
Dec. 27, 2014
Dec. 28, 2013
Sales Revenue [Line Items]        
Net Sales $ 456,207,000us-gaap_SalesRevenueNet $ 477,694,000us-gaap_SalesRevenueNet $ 1,008,411,000us-gaap_SalesRevenueNet $ 1,046,449,000us-gaap_SalesRevenueNet
General Mills Operations Llc [Member]        
Sales Revenue [Line Items]        
Net Sales     $ 138,034,000us-gaap_SalesRevenueNet
/ us-gaap_MajorCustomersAxis
= senea_GeneralMillsOperationsLlcMember
$ 150,345,000us-gaap_SalesRevenueNet
/ us-gaap_MajorCustomersAxis
= senea_GeneralMillsOperationsLlcMember