| Document and Entity Information | Nov. 12, 2019 |
| Cover [Abstract] | |
| Entity Address, Country | CA |
| Amendment Flag | false |
| Entity Central Index Key | 0000049938 |
| Document Type | 8-K |
| Document Period End Date | Nov. 12, 2019 |
| Entity Registrant Name | IMPERIAL OIL LTD |
| Entity Incorporation, State or Country Code | Z4 |
| Entity File Number | 0-12014 |
| Entity Tax Identification Number | 98-0017682 |
| Entity Address, Address Line One | 505 Quarry Park Boulevard S.E. |
| Entity Address, City or Town | Calgary |
| Entity Address, State or Province | AB |
| Entity Address, Postal Zip Code | T2C 5N1 |
| City Area Code | 1-800 |
| Local Phone Number | 567-3776 |
| Written Communications | false |
| Soliciting Material | false |
| Pre-commencement Tender Offer | false |
| Pre-commencement Issuer Tender Offer | false |
| Entity Emerging Growth Company | false |
