cm:Concept: us-gaap:DescriptionOfDiscontinuationOfInterestRateFairValueHedge
| Description of Discontinuation of Interest Rate Fair Value Hedge |
| us-gaap:DescriptionOfDiscontinuationOfInterestRateFairValueHedge |
| Description of discontinued fair value hedge relationships, including identification of hedged items and hedging instruments. Includes reasons for the discontinuation of the interest rate fair value hedge and the effects of the discontinuation on the financial statements. |
| cm:Concept |
| Text/String (xbrli:stringItemType) |
| For Period (duration) |
| (no balance type) |
| false |
| us-gaap:DescriptionOfDiscontinuationOfInterestRateFairValueHedge |