| Document and Entity Information | Nov. 19, 2020 |
| Cover [Abstract] | |
| Document Type | 8-K |
| Document Period End Date | Nov. 19, 2020 |
| Entity Registrant Name | Trilogy Metals Inc. |
| Entity Incorporation, State or Country Code | A1 |
| Entity File Number | 001-35447 |
| Entity Tax Identification Number | 98-1006991 |
| Entity Address, Address Line One | Suite 1150, 609 Granville Street |
| Entity Address, City or Town | Vancouver |
| Entity Address, State or Province | BC |
| Entity Address, Country | CA |
| Entity Address, Postal Zip Code | V7Y 1G5 |
| City Area Code | 604 |
| Local Phone Number | 638-8088 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Title of 12(b) Security | Common Shares |
| Trading Symbol | TMQ |
| Security Exchange Name | NYSEAMER |
| Entity Emerging Growth Company | false |
| Entity Central Index Key | 0001543418 |
| Amendment Flag | false |
