| Document and Entity Information Document | Oct. 29, 2020 |
| Document Information [Line Items] | |
| Document Type | 8-K |
| Document Creation Date | Oct. 29, 2020 |
| Document Period End Date | Oct. 29, 2020 |
| Amendment Flag | false |
| Entity Registrant Name | SunOpta Inc. |
| Entity Address, Address Line One | 2233 Argentia Road, Suite 401 |
| Entity Address, City or Town | Mississauga |
| Entity Address, State or Province | ON |
| Entity Address, Country | CA |
| Entity Address, Postal Zip Code | L5N 2X7 |
| Entity Incorporation, State Country Name | CA |
| City Area Code | (905) |
| Local Phone Number | 821-9669 |
| Entity File Number | 001-34198 |
| Entity Central Index Key | 0000351834 |
| Entity Emerging Growth Company | false |
| Entity Tax Identification Number | 00-0000000 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| NASDAQ [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Stock |
| Trading Symbol | STKL |
| Security Exchange Name | NASDAQ |
| Toronto Stock Exchange [Member] | |
| Document Information [Line Items] | |
| Title of 12(b) Security | Common Shares |
| Trading Symbol | SOY |
