Preferred Stock (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 27, 2020	Mar. 28, 2020	Jun. 29, 2019	Jun. 27, 2020	Jun. 29, 2019
Temporary Equity [Line Items]
Preferred stock accretion to redemption value	$ 423		$ 301	$ 748	$ 596
Dividends, Preferred Stock, Paid-in-kind	$ 1,700		0	$ 1,700	0
Series A Preferred Stock [Member] | Oaktree Organics, L.P. and Oaktree Huntington Investment Fund II, L.P.
Temporary Equity [Line Items]
Preferred Stock, Shares Issued	85,000			85,000
Preferred Stock, Value, Issued	$ 85,000			$ 85,000
Preferred Stock Issuance Costs	6,000			6,000
Preferred stock accretion to redemption value	$ 300		$ 300	$ 700	$ 600
Preferred Stock, Dividend Preference or Restrictions				In connection with the Series A Subscription Agreement, the Company agreed to, among other things (i) ensure SunOpta Foods has sufficient funds to pay its obligations under the terms of the Series A Preferred Stock and (ii) grant each holder of Series A Preferred Stock the right to exchange the Series A Preferred Stock for shares of common stock of the Company (the "Common Shares").  The Series A Preferred Stock is non-participating with the Common Shares in dividends and undistributed earnings of the Company.
Preferred Stock, Liquidation Preference Per Share	$ 1,000			$ 1,000
Preferred Stock Annualized Rate				8.00%
Preferred Stock, Dividend Payment Terms				Cumulative preferred dividends accrue daily on the Series A Preferred Stock at an annualized rate of 8.0% of the Series A Liquidation Preference prior to October 5, 2025, and 12.5% of the liquidation preference thereafter (subject to an increase of 1.0% per quarter, up to a maximum rate of 5.0% per quarter on the occurrence of certain events of non-compliance).  Prior to October 5, 2025, SunOpta Foods may pay dividends in cash or elect, in lieu of paying cash, to add the amount that would have been paid to the Series A Liquidation Preference.  After October 5, 2025, the failure to pay dividends in cash will be an event of non-compliance.
Dividends, Preferred Stock, Paid-in-kind	$ 1,700	$ 1,700
Preferred Stock, Liquidation Preference, Value	$ 86,700			$ 86,700
Convertible Preferred Stock, Terms of Conversion				At any time, the holders of Series A Preferred Stock may exchange their shares of Series A Preferred Stock, in whole or in part, into the number of Common Shares equal to, per share of Series A Preferred Stock, the quotient of the Series A Liquidation Preference divided by the Series A exchange price (such price, the "Series A Exchange Price" and such quotients, the "Series A Exchange Rate"). The Series A Exchange Price is subject to certain anti-dilution adjustments, including a weighted-average adjustment for issuances of Common Shares below the Series A Exchange Price, provided that the Series A Exchange Price may not be lower than $7.00 (subject to adjustment in certain circumstances). On April 24, 2020, in connection with the issuance of Series B-1 Preferred Stock pursuant to the Series B Subscription Agreement (see below), the Series A Exchange Price was reduced from $7.50 to $7.00. As at June 27, 2020 and December 28, 2019, the aggregate shares of Series A Preferred Stock outstanding were exchangeable into 12,385,714 and 11,333,333 Common Shares, respectively.
Preferred Stock, Voting Rights				In connection with the Series A Subscription Agreement, the Company issued 11,333,333 Special Shares, Series 1 to Oaktree, which entitles Oaktree to one vote per Special Share, Series 1 on all matters submitted to a vote of the holders of Common Shares, together as a single class, subject to certain exceptions. Additional Special Shares, Series 1 will be issued, or existing Special Shares, Series 1 will be redeemed, as necessary to ensure that the aggregate number of Special Shares, Series 1 outstanding is equal to the number of shares of Series A Preferred Stock outstanding from time to time multiplied by the Series A Exchange Rate in effect at such time.
Preferred Stock, Participation Rights				For so long as Oaktree beneficially owns or controls at least 50% of the Series A Preferred Stock issued on October 7, 2016, including any corresponding Common Shares into which such Series A Preferred Stock are exchanged, Oaktree will be entitled to (i) participation rights with respect to future equity offerings of the Company, and (ii) governance rights, including the right to approve certain actions proposed to be taken by the Company and its subsidiaries.
Special Voting Shares, issued and outstanding	11,333,333			11,333,333
Series B-1 Preferred Stock [Member] | Stock issued to each recipient [Member]
Temporary Equity [Line Items]
Preferred Stock, Shares Issued	15,000			15,000
Series B-1 Preferred Stock [Member] | Oaktree and Engaged [Member]
Temporary Equity [Line Items]
Preferred Stock, Shares Issued	30,000			30,000
Preferred Stock, Value, Issued	$ 30,000			$ 30,000
Preferred Stock Issuance Costs	3,200			$ 3,200
Preferred stock accretion to redemption value	$ 100
Preferred Stock, Liquidation Preference Per Share	$ 1,000			$ 1,000
Preferred Stock Annualized Rate				8.00%
Preferred Stock, Dividend Payment Terms				Cumulative preferred dividends accrue daily on the Series B-1 Preferred Stock at an annualized rate of 8.0% of the Series B-1 Liquidation Preference prior to September 30, 2029, and 10.0% of the liquidation preference thereafter (subject to an increase of 1.0% per quarter, up to a maximum rate of 5.0% per quarter on the occurrence of certain events of non-compliance).
Accrued Unpaid Dividends	$ 400
Convertible Preferred Stock, Terms of Conversion				At any time, the Series B-1 Preferred Stock may be exchanged, in whole or in part, into the number of Common Shares equal to, per share of Series B-1 Preferred Stock, the quotient of the Series B Liquidation Preference divided by $2.50 (such price, the "Series B-1 Exchange Price" and such quotient, the "Series B-1 Exchange Rate").
Convertible Preferred Stock, Settlement Terms				SunOpta Foods may cause the holders of the Series B-1 Preferred Stock to exchange all of their shares of Series B-1 Preferred Stock into a number of Common Shares equal to the number of shares of Series B-1 Preferred Stock outstanding multiplied by the Series B-1 Exchange Rate if (i) fewer than 10% of the shares of Series B-1 Preferred Stock issued on April 24, 2020 remain outstanding, or (ii) on or after April 24, 2023, the average volume-weighted average price of the Common Shares during the then preceding 20 trading day period is greater than 200% of the Series B-1 Exchange Price then in effect. At any time, if a holder of Series B Preferred Stock elects to exchange, or SunOpta Foods causes an exchange of Series B Preferred Stock, the number of Common Shares delivered to each applicable holder may not cause such holder's beneficial ownership to exceed 19.99% of the Common Shares that would be outstanding immediately following such exchange (the "Series B Exchange Cap").
Number of common shares available due to exchangeable preferred stock	12,000,000			12,000,000
Preferred stock exchange, description of exchange price				The Series B-1 Exchange Price is subject to certain anti-dilution adjustments, including a weighted-average adjustment for issuances of Common Shares below the Series B-1 Exchange Price, provided that the Series B-1 Exchange Price may not be lower than $2.00 (subject to adjustment in certain circumstances).
Series B Preferred Stock [Member] | Oaktree and Engaged [Member]
Temporary Equity [Line Items]
Convertible Preferred Stock, Terms of Conversion				Oaktree and Engaged will be entitled to vote the Series B Preferred Stock with the Common Shares on an as-exchanged basis, subject to a permanent 19.99% voting cap. As a result of the voting cap, each of Oaktree and Engaged will only be able to vote its Series B Preferred Stock to the extent that, when taken together with any other voting securities each investor controls, such votes do not exceed 19.99% of the votes eligible to be cast by all security holders of the Company.  On April 24, 2020, the Company designated Special Shares, Series 2 to serve as the mechanism for attaching exchanged voting to the Series B Preferred Stock.  The Special Shares, Series 2 entitle the holder thereof to one vote per Special Share, Series 2 on all matters submitted to a vote of the holders of Common Shares, voting together as a single class, subject to certain exceptions.  The Special Shares, Series 2 are not transferrable and the voting rights associated with the Special Shares, Series 2 will terminate upon the transfer of the shares of Series B Preferred Stock to a third party, other than an affiliate of Oaktree or Engaged, as applicable.  On April 24, 2020, 6,000,000 Special Shares, Series 2 were issued to Engaged, equal to the number of Common Shares issuable to Engaged on the exchange of all of the shares of Series B-1 Preferred Stock held by it, and no Special Shares, Series 2 were issued to Oaktree, as Oaktree was subject to the Series B Exchange Cap.Under the terms of the Series B Subscription Agreement, the Company had the right, but not the obligation, to require each of Oaktree and Engaged to purchase its proportionate share of up to 15,000 shares of Series B-2 Preferred Stock for aggregate consideration of up to $30.0 million, and up to 30,000 shares total, by giving notice to Oaktree and Engaged on or before July 15, 2020.  The exchange price for the Series B-2 Preferred Stock would initially have been that amount which was equal to a 30% premium to the 15-day volume-weighted average price of the Common Shares determined as at the date of notice, provided that such exchange price could not be less than $2.00 or greater than $3.50 per underlying Common Share.  The Company elected not to exercise this option, and no shares of Series B-2 Preferred Stock have been issued.