Commitments and Contingencies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 26, 2020	Sep. 26, 2020
Loss Contingencies [Line Items]
Payment for cash settlement	$ 4.4	$ 4.4
Product Recall [Member]
Loss Contingencies [Line Items]
Loss Contingency Damages Sought		On November 20, 2017, Treehouse Foods, Inc., several of its related entities, and its insurer filed a lawsuit against the Company in the Circuit Court of Cook County, Illinois, titled TreeHouse Foods, Inc. et al. ("TreeHouse") v. SunOpta Grains and Food, Inc.  The Company was served with the Summons and Complaint on January 24, 2018.  After the Company removed the case to the United States District Court for the Northern District of Illinois, the plaintiffs filed an Amended Complaint on April 23, 2018, and a second Amended Complaint on October 12, 2018.  The plaintiffs alleged economic damages resulting from the Company's 2016 voluntary recall of certain roasted sunflower kernel products due to the potential for listeria monocytogenes contamination.  The plaintiffs brought claims for breach of contract, express and implied warranties and product guarantees, negligence, strict liability, negligent misrepresentation, and indemnity seeking $16.2 million in damages.  There were no allegations of personal injury.  On March 29, 2019, the court dismissed the plaintiffs' claims for negligence, strict liability, negligent misrepresentation, and common law indemnity.  On May 31, 2020, the court granted summary judgment to the Company on TreeHouse's claims for breach of contract and breach of product guarantees, but denied summary judgment on TreeHouse's claims for breach of express and implied warranties.  On the remaining claims, the court limited TreeHouse's damages to the purchase price of the product the Company sold to TreeHouse.  On September 14, 2020, the Company entered into a Confidential Settlement Agreement and Mutual Release (the "Settlement Agreement") with TreeHouse.  The Settlement Agreement resolved the disputed issues among the parties in connection with the litigation filed by TreeHouse against the Company, as described above.  Pursuant to the terms of the Settlement Agreement, the Company paid TreeHouse $4.4 million.  On September 18, 2020, the parties filed a Stipulation of Dismissal with prejudice and the court entered a corresponding order dismissing the litigation with prejudice.
Loss Contingency Damages Sought Value		$ 16.2
Payment for cash settlement		$ 4.4