Earnings per Share - Summary of Earnings Per Share (Parenthetical) (Detail) - $ / shares	12 Months Ended
Oct. 31, 2025	Oct. 31, 2024
Earnings per share [abstract]
Outstanding options excluded from calculation of diluted earnings per share	0	2,551,540
Weighted average Exercise price of average outstanding share options excluded from the calculation of diluted earnings per share	$ 0	$ 70.05

Weighted average exercise price of average outstanding share options excluded from calculation of diluted earnings per share.

No definition available.

Name:	cm_WeightedAverageExercisePriceOfAverageOutstandingShareOptionsExcludedFromCalculationOfDilutedEarningsPerShare
Namespace Prefix:	cm_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration