cm:Concept: us-gaap:IncreaseDecreaseInFairValueOfHedgedItemInPriceRiskFairValueHedge1
| Increase (Decrease) in Fair Value of Hedged Item in Price Risk Fair Value Hedge |
| us-gaap:IncreaseDecreaseInFairValueOfHedgedItemInPriceRiskFairValueHedge1 |
| Amount of unrealized gain (loss) recognized in earnings related to the fair value of the hedged item in a price risk fair value hedge, offset by the gain (loss) on the hedging instrument to the extent that the fair value hedge is determined to be effective. |
| cm:Concept |
| Monetary (xbrli:monetaryItemType) |
| For Period (duration) |
| Credit |
| false |
| us-gaap:IncreaseDecreaseInFairValueOfHedgedItemInPriceRiskFairValueHedge1 |