Bank Indebtedness and Long-Term Debt (Narrative) (Details) $ in Thousands, € in Millions	1 Months Ended		6 Months Ended
	Oct. 22, 2018 USD ($)	Sep. 19, 2017 USD ($)	Jun. 27, 2020 USD ($)	Jun. 27, 2020 EUR (€)	Jun. 27, 2020 USD ($)	Oct. 20, 2016 USD ($)
Debt Instrument [Line Items]
Lessee, Finance Lease, Lease Not yet Commenced, Description			The Company has commitments under certain master lease agreements that provide for up to approximately $35 million of financing in the aggregate related to the addition of new plant-based beverage and ingredient extraction processing and packaging equipment.  As at June 27, 2020, the related finance leases had not commenced, and no amount of right-of-use assets, or lease liabilities, were recognized on the consolidated balance sheet as of that date.
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Initiation Date			Feb. 11, 2016
Line of Credit Facility, Maximum Borrowing Capacity					$ 350,000
Line of Credit Facility, Description			On February 11, 2016, the Company entered into a five-year credit agreement for a senior secured asset-based revolving credit facility with a syndicate of banks in the maximum aggregate principal amount of $350.0 million, subject to borrowing base capacity (the "Global Credit Facility"). The Global Credit Facility is used to support the working capital and general corporate needs of the Company's global operations, in addition to funding future strategic initiatives.  The Global Credit Facility also includes borrowing capacity available for letters of credit and provides for borrowings on same-day notice, including in the form of swingline loans. On January 28, 2020, the credit agreement was amended to, among other things, extend the maturity date of the Global Credit Facility to March 31, 2022.Individual borrowings under the Global Credit Facility have terms of six months or less and bear interest based on various reference rates plus an applicable margin. The margin ranges from 0.25% to 0.75% with respect to base rate and prime rate borrowings and from 1.25% to 1.75% for eurocurrency rate and bankers' acceptance rate borrowings. In connection with the amendment of the credit agreement on January 28, 2020, the applicable margin rate on any loans under the Global Credit Facility (including the U.S. Subfacility, as described below) is increased by an additional 0.50% while the Company's total leverage ratio exceeds a specific threshold.
Line of Credit Facility, Expiration Date			Mar. 31, 2022
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period			0.25%
Revolving Credit Facility [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period			0.75%
Revolving Credit Facility [Member] | Prime Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period			1.25%
Revolving Credit Facility [Member] | Prime Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period			1.75%
US Subfacility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 20,000
Line of Credit Facility, Description			On September 19, 2017, the Company entered into an amendment to the Global Credit Facility to add a $15.0 million U.S. asset-based credit subfacility (the "U.S. Subfacility").
Line of Credit Facility, Increase (Decrease), Net		$ 15,000
Line of Credit Facility, Date of First Required Payment	Mar. 31, 2019
Line of Credit Facility, Periodic Payment, Principal		$ 3,330
Line of Credit Facility, Interest Rate Description			Borrowings under the U.S. Subfacility bear interest based on various reference rates plus a margin based on average borrowing availability for the preceding fiscal quarter, ranging from 2.00% to 2.50% with respect to base rate and prime rate borrowings and from 3.00% to 3.50% for eurocurrency rate and bankers' acceptance rate borrowings.
Drawdown credit facility					$ 3,330
US Subfacility [Member] | Base Rate And Prime Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.00%	2.00%
US Subfacility [Member] | Base Rate And Prime Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				2.50%	2.50%
US Subfacility [Member] | Eurocurrency Rate And Bankers Acceptance Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.00%	3.00%
US Subfacility [Member] | Eurocurrency Rate And Bankers Acceptance Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				3.50%	3.50%
Global Credit Facility [Member]
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate				2.95%	2.95%
Bulgarian Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity | €				€ 6.0
Line of Credit Facility, Interest Rate During Period			2.75%
Senior Secured Second Lien Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage						9.50%
Debt Instrument, Description			On October 20, 2016, the Company's subsidiary, SunOpta Foods Inc. ("SunOpta Foods"), issued $231.0 million of 9.5% Senior Secured Second Lien Notes due 2022 (the "Notes").
Debt Instrument, Issuance Date			Oct. 20, 2016
Debt Instrument, Face Amount					$ 223,500	$ 231,000
Debt Instrument, Redemption, Amount			$ 7,500
Debt Instrument, Frequency of Periodic Payment			Interest on the Notes is payable semi-annually in arrears on April 15 and October 15 at a rate of 9.5% per annum.
Debt Instrument, Maturity Date			Oct. 09, 2022
Debt Instrument, Redemption, Description			At any time after October 9, 2019, SunOpta Foods may redeem the Notes, in whole or in part, at a redemption price equal to 104.750% from October 9, 2019 through October 8, 2020, 102.375% from October 9, 2020 through October 8, 2021 and at par thereafter, plus accrued and unpaid interest, if any, to but excluding the date of redemption.  Certain additional redemption rights were applicable prior to October 9, 2019.  In the event of a change of control, SunOpta Foods will be required to make an offer to repurchase the Notes at 101.000% of their principal amount, plus accrued and unpaid interest, if any, to the date of purchase.The Notes are secured by second-priority liens on substantially all of the assets that secure the credit facilities provided under the Global Credit Facility, subject to certain exceptions and permitted liens.  The Notes are senior secured obligations and rank equally in right of payment with SunOpta Foods' existing and future senior debt and senior in right of payment to any future subordinated debt. The Notes are effectively subordinated to debt under the Global Credit Facility and any future indebtedness secured on a first-priority basis.  The Notes are initially guaranteed on a senior secured second-priority basis by the Company and each of its subsidiaries (other than SunOpta Foods) that guarantees indebtedness under the Global Credit Facility, subject to certain exceptions.The Notes are subject to covenants that, among other things, limit the Company's ability to (i) incur additional debt or issue preferred stock; (ii) pay dividends and make certain types of investments and other restricted payments; (iii) create liens; (iv) enter into transactions with affiliates; (v) sell assets; and (vi) create restrictions on the ability of restricted subsidiaries to pay dividends, make loans or advances or transfer assets to the Company, SunOpta Foods or any guarantor of the Notes.  The foregoing covenants are subject to certain threshold amounts and exceptions as set forth in the indenture governing the Notes.  In addition, the indenture provides for customary events of default (subject in certain cases to customary grace and cure periods), which include nonpayment, breach of covenants in the indenture, certain payment defaults or acceleration of other indebtedness, a failure to pay certain judgments and certain events of bankruptcy and insolvency.  If an event of default occurs and is continuing, the trustee or holders of at least 25% in principal amount of the outstanding Notes may declare the principal of and accrued and unpaid interest on, if any, all the Notes to be due and payable.As at June 27, 2020, the estimated fair value of the outstanding Notes was approximately $224 million, based on quoted prices of the most recent over-the-counter transactions (level 2).
Debt Instrument, Interest Rate, Effective Percentage				10.40%	10.40%
Line of Credit Facility, Fair Value of Amount Outstanding					$ 224,000
Senior Secured Second Lien Notes [Member] | from October 9, 2019 through October 8, 2020
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage			104.75%
Senior Secured Second Lien Notes [Member] | from October 9, 2020 through October 8, 2021
Debt Instrument [Line Items]
Debt Instrument, Redemption Price, Percentage			102.375%