Cover Page	3 Months Ended
	Mar. 31, 2020 shares
Cover [Abstract]
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Document Transition Report	false
Entity Central Index Key	0000049938
Current Fiscal Year End Date	--12-31
Document Quarterly Report	true
Entity Registrant Name	IMPERIAL OIL LTD
Amendment Flag	false
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	0-12014
Entity Small Business	false
Entity Incorporation, State or Country Code	CA
Entity Emerging Growth Company	false
Entity Address, Address Line One	505 Quarry Park Boulevard S.E.
Entity Tax Identification Number	98-0017682
Entity Address, City or Town	Calgary
Entity Address, State or Province	AB
Entity Address, Country	CA
Entity Address, Postal Zip Code	T2C 5N1
City Area Code	1-800
Local Phone Number	567-3776
Entity Common Stock, Shares Outstanding	734,076,755