Financial and derivative instruments - Summary of realized and unrealized gain or (loss) on derivative instruments (Detail) - CAD ($) $ in Millions	3 Months Ended
Mar. 31, 2024	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Revenues	$ (24)	$ (23)

Total realized and unrealized revenue on derivative instrument.

No definition available.

Name:	imo_RealizedAndUnrealizedRevenueOnDerivativeInstrument
Namespace Prefix:	imo_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration